I would crop the top a little, maybe a 1/3 of the part above the chair. But i like it. Wish he'd been barefoot. I think that would have been a nice addition.
This is a great portrait. Its an awesome change from the boring studio stuff I always see. It looks perfectly natural (I hate poses that look forced) The comp is perfect. Without the top all of the fun color would be lost and without the bottom, the shot wouldn't have enough balance. Good job!