Nit-picky is perfect, thank you so much. Sometimes it can be hard to get solid critiques from people. (: I think I tried too hard to keep the color count where it was. I had a hard time choosing the colors for the sky, and I was hesitant to use the dark purple for precisely that reason. I see what you mean with the spine. :\ The sky was rushed compared to the rest of it too, so the messy linework doesn't surprise me. I was at a loss for what to do with it.

I outlined the arm cause I thought that defining the shape was important... so I went for that instead of adding a darker color for contrast to fix the problem. May not have been worth it tho.

Thank you for your time. (:

To be a bit nit-picky, the sky has alot of jaggies and feals like it has very messy linework compared to the rest of the peice. The dark colors of the bigger monster's spines also blends in with the sky (because they are matching colors), it adds a bit of confusion with the dithering on one of the spines, it looks like its evaporating into the sky. The right arm of the darker monster also has a very strong contrast due to that thin purple line that outlines the arm. Im not sure what there is to say about it besides it does take alot of focus because it seems a bit out-of-place compared to the rest of the monster's design. 

I think you have a good color selection going and good control of the lighting, looking at the blue-pokemon and the rocks. I like to composition too.