There is definitely an art to painting camo so it looks good on models. You can go more random as poda_t mentioned, my main suggestion with "random" is that it still needs to be somewhat ordered to look good. Choose how thick your bands or blobs are going to be and how much of the below colour you want shining through and then try to stick to that across the whole model, so even though the bands might be random, the spacing between them is somewhat consistent.
A good example is WW2 planes, or the Thunderbolt on the cover of the Imperial Armour masterclass book...
http://www.forgeworld.co.uk/Modelling-Supplies/IMPERIAL_ARMOUR_MODEL_MASTERCLASS_VOLUME_TWO.html
Note the camo is quite random, but the size of blobs and the spacing is actually rather consistent, so there's no areas which are just purely one colour of the other and no areas with more or less detail.
Another option is to go more ordered. Something like this looks really good but is actually just strips sprayed equidistant...
http://www.forgeworld.co.uk/Warhammer-40000/Imperial_Navy/MARAUDER_DESTROYER.html
Or this tank on the front of another forge world book, not as ordered, but still for the most part it's quite ordered.
http://www.forgeworld.co.uk/Images/Product/DefaultFW/xlarge/imparmour5.jpg
Have a look at images of camo on vehicles and pay close attention to how the bands and blobs are painted, you'll notice that it's not quite as simple as throwing down randomness.
You also have colour selection, I'm not really good at colour theory so I'm not going to make any suggestions other than to say the brown and blue does look a bit odd to me, though maybe it's just the gloss.