Your clean linework here works really nicely.

Some thoughts for next time.

Your hand is about as "tall" as your face is, right? Right. And...with perspective, things that are closer to you get bigger. Right? Right.

So, a hand that is closer to you than the face, should be bigger than the face, right?

Right now, the hand would be the perfect size if it were right next to his head. But since it's so much closer to us than the head is, it should probably be bigger. Plus, it'll give a bigger impact to the action he's doing!

But I realize this is a finished piece...so it's just thoughts to keep in mind for later.

I also would've liked to've seen more of his shoes/feet. Right now, it kind of looks like his feet just disappear. And...and that's freaky. No, really.

But anyway--congratulations on your commission! :)