Need some advice:
1)About hand
2)About how face can be in this image
3)Shading...
Well, I would start with getting some better contrast in the colors... maybe make some of them more saturated too, like the hair for example.
But I also think you need a solid light source. Right now, it SEEMS like the light should be coming to the right and somewhat behind him. (Based on how the arm is shaded. But then, the head doesn't fallow the same light sourced as the arm. I suppose it could be coming from the left behind him a bit, but then his chest needs to be darker too. So, you should pick where the light is coming from.
It also seems to me that his head isn't in proportion with his ears... those ears are somewhat small and up too high.
I just googled for this real quick, and the image quality is terrible, and it's a woman, but it should still help:
I'm sure someone will come along and do a neat sketch to better show these points, if this doesn't do it. But you can at least use this to get a good feel to where to put the features.
Now looking at the hand, I'd say you intend that he should hold the pen, as if he were to write with it, right? So, holding it up like Sam-uk suggested probably isn't what you hand in mind. Personally, I've always found that pose for the hand is a pain in the ass to draw or pixel, but here's a decent reference for you:
Given the angle, you might want to move his arm down... but you could flip around that ref and see if it helps some. And I think before you go in and add nails, which can also make it look odd if you don't do it right, you should get the hand down. I'd avoid using pink for for the nails though, since it seems to girly. You'll probably want to use the skin tones to show them very subtly.
Good Luck!