The arms and legs look a little stickish. I understand your going for the skinny look, but there needs to be a little more defintion regardless. Here are some of my own thoughts:

1) Make some calves, there needs to be some muscle there. Maybe stretching a few polys out could help.

2) Make the biceps and forearms slightly more defined and possibly keep the elbows the same.

3) The head seems really large in comparison to the body. I understand it is supposed to be big, but even so, there may be a point at which it is too big.

These are just some thoughts of mine. Just try to experiment with a few things, push and pull some polys, etc.

P.S. How many Polys did you use?