Without giving an official critique, I would say that the only things that would need improvement from a quick glance would be some details on the door. I think the scribbles in the semi-circle grooves in the door that are just right of the character's shoulder should have been more detailed along with the center of the "X" in the upper middle part of the door. It looks sloppy and I think a few extra minutes flushing them out and making them looked more defined would add a lot to the picture. Everything else from the character to the rest of the scenery looks great.
Thank you Abellius for the interesting comment! You're absolutely right, I would have spent more time on his boots as well, unfortunately I had to work on a very very tight deadline and I had already spent too much time on it