Wow, that's a damn fine job for MSPaint!
Couple problems, however. The main one that's really marring this is some pretty wonky perspective on the head. I think the issue here is that you're trying to show us too much of the side farthest from us, leading to a distorted perspective and a blocky, rectangular head. The back of his skull ought to be a bit more rounded, and his jaw should drop at an angle, not straight down as you have it.
I'm not very good at draw-overs, but I did this to try and show you what I mean better...
The other issue is that his hand closest to us looks really flat. I'm having a hard time pinpointing and putting the issue into words, but I think a lot of it has to do with the shape of the shadow it casts. I don't think it should be right behind the hand like you have it.
But still. Damn.