Gavalcraw: rather than triple post, just hit 'edit' and alter your original comment.

interesting piece, but I agree with 1ucas about the stationary eye.

kind of has a punk skater art feel  to it

 Thanks for comment!

Eye is completely static because it is a damage center (weakest point) of the boss. In the game, when you shoot in eye, it has an animation of damage. Also eye has an animation of turning into a mouth. I think blinking animation in the game is not neccessary. 

I drew this mutant with NES palette to make it look like 8-bit. It has not much colors to work with.

You should make the eye move. Having it completely static is such a waste of potential.

Make it look around and blink, it'll look pretty good.
 

Also, going for more pastel tones usually makes some things look more organic. The green part, for instance, would look better with a sicklish pastle green with dark purple-ish veins on it. Just my opinion, of course.