i think even just a super-faint outline of part of his nose on the left would be enough, I hate trying to give shape to objects using just shading...
what i really like about it is the proportions are all very accurate and the folds on his Keffiyeh (i think you had it right, flyman) are rendered well. The only departure from the actual photo is his eyes are spaced slightly differently, which gives him a look more like he's staring into space than looking straight out from the image. I think he looks more thoughtful that way.
either way nicely done
