Very nice!!! The only thing I could think to mention is that I'd like to see some definition in the teeth. His molars I think should be slightly darker than his front teeth, just to give some depth to his mouth. I love the use of texture in this piece. It really helps to give what would otherwise be a flat, but nifty, piece some visual interest.

I have 33 words left. I hate this 100 word minimum. I think this and your Wolvie piece would make great POP art-style prints. Do them up in 24"x36" Panels, and I could see them adorning my wall.