heh! thought it was a duck at first!
Cool but what happened the effort on the background? It looks slapped in compared to the nice character and skull! The green mans pose is a bit awkward, (one closed fist, one open, one hand forward, one back etc), the muscle under the right arm looks like a pec (chest muscle), needs shifted left if it is or tweaked a tad otherwise. Keep working on this, looks like you're onto something good
MUY BUENO :)