Nice picture! I really like the coloring job you did, the shading and the way the light reflects off the character, it looks really good.

Also, you've done a wonderful job with the musculature on his body, very nice! I only have one pick about it (I hope you don't mind). If he is that skinny then you should be able to see his "six pack" muscles on his stomach. They don't have to be weight-lifter quality defined, but you can usually kinda see them.