This is really well done. Yoo've captured all of the details really well, especially the facial hair. A lot of people dont take the time necessary to make hair look like hair. On the other hand, I would suggest putting something in the background, even if its just a field of grey. You put a lot of work into the figure and the brightness of the background can be a little distracting from that. The viewers eyes will follow where he is looking, and then keep on going off the piece. They need something there that will keep their gaze trapped within the composition and bring it back to what's important in the drawing.