I'm not a terribly knowledgeable artist but just one quick thing I noticed from what you could call an "outsiders" perspective. I first saw this picture when it didn't have the shirt or the background. I feel like the background is good but i find that the shirt is maybe not in as much detail as the rest of the picture. It almost has an unfinished quality to it, not just out of focus. I would add some more contrast and detail like you do with the face and hand. Overall I find this to be an extraordinary drawing. It just needs to be a little more consistent in the level of detail. Great job though!