A couple points; But overall would just like to say how much I love it, the face in the side door looks awesome, looks like its in total agony!
The mouth arm coming out of the roof looks like the teeth could do with a brown wash. to highlight the gaps in the teeth. I would suggest agrax earthshade, followed by a very small red wash between the lips and base of the teeth (its a trick I have found that really makes mouths look fleshy without much hassle).
I also second the idea of some more browns in the deeper recesses of your nurle rot/flesh work. You want to frame all those pustules and make them stand out. Another colour that would work well would be a purple. Heres what I mean;
So as you can see, purple and fleshy reds in crevasses works really well. Now Im not saying I don't like what you've already done, but I really think with a little wash work you could achieve a really fantastic and varied colour palette within the flesh work. Perhaps a good place to start would the mouth of the face on the side door. Do a light wash with a red/purple/pinky flesh tone and see what you think.