You could look at the head--if that's a head--in a few different ways, and all of them are unnerving. This is a solid, well-done picture, especially considering it's a study.

The light up top works really well; the shadows and highlights on the torso look great. However, once I get down to the abdomen and pelvis, it fells like, with that much light above, the shadow shouldn't be as dark as it is, especially when the spikes are partially highlighted. Looking at it a little closer, it may just be my monitor, but it looks like the painting style in that area is different as well. Was this intentional? Was the abundance of shadow intentional? That doesn't bother me as much as the shift in style, so I'm gonna say the shadow thing is fine.

I'm not adept at art myself, so in the end, your judgment is probably better than mine.