I'd say the only thing I think that needs revising would be his left ear.
The shape looks different and the shading doesn't look as well done as the shading you did on his face and accentuating his cheekbones. The light hits the upper bridge of the ear producing a fine line but yours is flatter and less striking.
I am not the best drawer so feel like a dick saying this but your pic is fab and only needs minor adjustments to be considered pretty perfect imho!
First of all thanks for posting your artwork for us to enjoy. This is definitely a great piece of artwork and it's quite a nice technique that you've used here to create a rather skillful piece of work. With regards to improving this, you should look to rework the left ear as someone has said above, but I also feel that you should perhaps look at the eyes again. There is an emotion there which I don't feel that you've quite captured from the photograph. You've got an emotion, but it's more sadness, than what is in the photo. I'd also advise you to consider how you might now use this piece of work. Could you use it as a study for a much larger piece of work.
An excellent drawing, with just a few tweaks needed.