OK, critique time. I wrote these a while ago, as I went through deciding who should get my vote. I didn't post it earlier as I didn't want to influence anyone's voting.
A quick disclaimer first, I have tried to pick out any and all issues that I could see for each piece. It's meant to be constructive criticisms, so apologies if anything comes across as harsh. This is just what I think could have improved your piece for this competition.
First up...
Cultists.
Desubot:
Whereas most of us thought of random industrial lumps of metal for our junk, you caught on the something closer to home. Very good idea.
That it's all scratch-built is even more impressive. It's a shame you didn't get the workings on the back of the fridge though. The damage to the door is good and I really like the sink.
The painting is pretty good. The wood is nicely done. Good effort on the marble. The weathering is good, but the inside of the fridge could have been dirtier to match the outside and the setting. The sandwich and bottle are good too.
Gawdamsumbish:
Nice pile of junk with a good collection of pieces with both a good variety in texture and colour.
Your weathering is good, but some of the painting could be neater and looks like you could thin your paints a little more.
Good effort on the mattress, the springs sticking out are a nice touch. I think if the blue lines had been neater and a little faded it would look even more realistic. I like the traffic cone too.
GrimDork:
Very ingenious idea and I like the use of a motor electromagnet as the portal gate (I had the wires out of one of them and they've proved very useful too

).
I can just imagine the other gate buried in a junk pile and as things are piled on top, a little more is pushed through here.
The selection of junk pieces are good and they work well.
The painting of the metal and rust is good, but the weathering of the portal could be improved to look less painted on (possibly with some washes etc.) and the patches are a little too evenly distributed.
I like the wires and cables you added to the closed side, but if the wires aren't attached how is it working... or is it not working and people have just been ramming junk into it and wondering why it's not disappearing... (thought provoking

)
Llamahead:
First off it's tricky to give a good critique from the pictures as they're not all in perfect focus and there's quite a bit of glare which hides details.
However, I hail your use of sprue, always good to see.
Your rust painting looks quite good with some nice tones and looks natural.
The overall piece could have done with a bit more variation from some more different pieces and colours. Some plant life would have really helped this.
Snrub:
While the use of a plain white background is generally a good thing for photos, when your subject is dark, it can make it loose contrast and details are difficult to make out.
As a terrain piece, it works quite well. There is a nice selection of bits, but it could do with some smaller pieces of junk between the large main bits and the small rocks of the base.
The painting and weathering looks good, but the polystyrene foam looks a little too cartoon-like to match the other bits there.
Aspiring Champions.
Andy_T:
Nice little pile of junk.
The selection of pieces is good. Nice range of textures.
I really like the rust tone you have there, but it would've been nice to have a bit more variation in the colour on the different pieces.
I like the worn paint on the blue thing, could have done with more of that or another colour somewhere, but I like it.
Camkierhi:
Good use of parts. Nice selection of bits.
Very good range of colours with reds, blues, yellows and greens.
The dirt and weathering are good, but some of the rust could be improved by making it look less like it was painted on (in particular on the large cog), possibly by some washes while the paint is wet or my adding the paint onto a wet surface, so it runs and bleeds and blends naturally (let it work for you, don't force it

).
Nice pile of junk and I love the sign.
Littletower:
I like the fence and the barbed wire. The aluminium foil barrel is really good and it's nice to see a sprue flower (not just a basic sprue plant, but a more difficult flower

).
The flower could have done with a little company (like a patch of grass it's growing out of) so it's not just a random flower that's growing where nothing else can.
The painting is very nice. Really like the rust tones you've done, especially the barrel.
Could have done with some smaller rubble/rocks to tie the bits to the base and give the base some more texture.
Scarper:
Really like the bus shelter, looks great all round.
The painting and weathering is great. Love the colours and the graffiti. The addition of the route-map and the "missing" posters really give it a past.
The broken window is also done very well.
The junk is quite ordered, which is not wrong, just different. Some of the pieces look a bit too clean though. I like the tools you made too.
Could also have done with a little bit of dust/dirt/rubbish collected in the corners to tie it to the base.
Daemonhunter187:
I like the burnt out box, that looks very good.
The painting and weathering is also good. Some of the rust on the more upright pipe could have worked better with a little texture to the surface.
I like the pieces you used to make the pile, but there's something about the arrangement that feels off, but I'm not sure what it is. I still like it though.
hdbbstephen:
While it has both junk and a pile (of skulls), it doesn't say "junk pile" to me. However, as a terrain piece, it is good.
The painting and weathering is good, although the hazard stripes could be straighter. I like the bubbled/chipped paint with the rust coming through.
jedi76:
Like Meade, some larger pics would have been nice.
Nice little junk pile, I like the bottles and there is a good selection of bits.
The painting is good. I like the dulled rusty colour that keeps the metal sheen.
Can't really add anything, good job.
sennacherib:
I don't know what it is, or what it was. But I like it.
The painting is good. Some of the streaks could look a bit more natural and the patches of orange rust are a bit too evenly spaced on the green thing.
The actual junk pile is good. Nice variation in pieces, with metal, wood, bricks and a body (am I to assume you sculpted that yourself? Good effort, I know how hard things like hands can be on this scale. A little more work is needed to get all the anatomical features correct, but keep at it).
While the metal pieces are nicely detailed and dirtied, the wood and bricks could do with a bit more attention (highlights and dirt).
Weetyskemian44:
I know you didn't have the time you would have liked to have spent on this. It is one of the junk constructs and doesn't say "junk pile" to me. But, as usual, it is very nicely painted. I like the dirt/rusty tone and the brass is very nice.
Could have done with more little pieces of junk as you intended.
It's a cool little piece that would work well in any industrial setting.
Exalted Champions.
Chelnov:
I like the happy acid face concept that is only visible from above, clever idea. I like the use of pipes for the eyes, maybe you could have used a curved piece of junk for the mouth, but good and fun none-the-less.
The selection of bits are good. They are not quite recognisable but familiar shapes that give it realism.
The painting is good, but in places could do with a little refinement from additional shading or blending. The cracks on the yellow look painted on and a little highlighting on the edges would help sell them more as cracks and in places the yellow doesn't look as if it's covered a darker undercoat, that could have been disguised with a little dirt. (unless you are trying to make those bits look painted...).
Nice pile of junk.
Dr H:
A lovely work of art, of course...
Probably could have done with a few more different materials in addition to the rusty metal.
Some of the orange rust patches could have been done better and look less painted.
The addition of plant life would have worked nice with the setting, but my usual grass material was outside of my, self imposed, material limitations.
The concept is, of course, brilliant...
Moltar:
I like the variety of colour in this piece. Makes it stand out from the rusty entries.
Nice collection of pieces that work together as a pile of junk. The coil of wire looks a little clean relative to the rest.
The patches of grass, like Brian's, add to the long deserted feel of the pile.
The painting is good, but could be a little smoother in places.
Rabid Ferret:
Very nice painting from the large brass pipe to the tiny details on the broken fresco and beer can. The weathered yellow paint is what I was intending to do on the large pipe in my piece, but I couldn't get it to look right and was not going to be anyhere near as good as yours.
The selection of bits are good but could probably have done with a few more pieces of junk to make it more of a pile. Other than that, can't fault it.
Theophony:
Nice idea. One man's junk is another's dead body...
Some of the detail is difficult to pick out in the photos, but the bags look good and the painting on the sign looks perfectly on the good side of "scale" bad painting and not painter (you) bad painting, a difficult thing to pull off.
The bits of rust look pretty good. The green thing could have been a little dirtier and so could the bags.
hk1x1:
One of the junked things built from junk pieces. Having said that, it is a very nicely built robot made from junk (I also liked the crane that you also made

). I like the way it looks like it was sat down and turned off ages ago and hasn't moved since, the only person interacting with it was to remove an arm.
Nicely painted, good level of dirt and grime. Good job.
inmygravenimage:
I like the workshop concept and choice of bits work well. You can just imagine little stories of the owner working on the pieces there.
Nicely painted as a very grubby collection of junk. The fleur could have done with being made to "look" heavier. Either by being sunk into to ground a little more or having something more substantial supporting it (or deforming the fence).
I like the irregular shape of the base too.
Monkeytroll:
The other workshop... Still a nice concept. And very nicely built.
I like the matchstick fence and the supporting beam and shelf with their brackets are brilliant.
The inclusion of all the little bits is nice, you can spend quite a while looking at it and still find a new bit.
It's also been a long time since I've seen some scalextric bits.
The painting and weathering are very nice and a good selection of colours and textures. The sign is cool too.
Lords.
BrianCJ:
I love the meadow setting of the piece. Gives a nice contrast of colour between the green and the rust and adds to the sense of abandoned junk being reclaimed by nature.
I like the faded hazard stripes on the pipe in the middle, but the smaller stripes on the other thing look a little rushed (considering you built the whole thing in 3 hours, that's probably the case, so fair enough).
I like the little blue thing. It adds a different element to the whole.
The rust and weathering are good. Can't fault it.
Coming back to the grass, I think it could have done with more variety in length. There's the long clumps from between the junk pieces and then the rest is short. It needs some patches in-between to give it a more natural feel.
Nerdfest09:
A nice industrial feel to the whole piece. Will definitely fit in to your up-and-coming ZM board.
I like the story element you have to it and it looks exactly like what you have described (the destroyed generator).
Nice selection of bits, although including a few pre-fab' bits, they do sell the piece and it wouldn't be without them.
Painting is nice (as expected) and I really like the glowing bits.
This is one of the pieces that is more a "junk construct" and not a "pile of" junk, which was one thing that I didn't think was the point of the contest, but you're not alone and it's not a problem.
OneManNoodles:
Looks nice and I like the addition of the pillar to be a "place" where junk has been piled up.
The painting and weathering all over are very good. I like the streaks on the pillar and green tank thing.
The old-looking computer is a nice touch, could only be surpassed by an old-looking printer...
While it could do with more pieces of junk on the pile, it doesn't feel incomplete or missing of anything. Good job.
Meade:
The painting, weathering and construction are all pretty much perfect as far as I can tell. Really, really nice.
Definitely one of the piles of junk pieces and, like OneManNoodles, the addition of something for the junk to be piled up against is nice.
The inclusion of the bones/skull and a locker door(?), while pre-fab', do add a nice touch of realism to the piece.
I like the faded/chipped cog symbol on the wall, that's very nicely done.
Could have done with more bigger pictures to look at though.
Struggling to find any faults with it.
Good job again to everyone.
Hope my comments help.