Its pretty minor.
On the left side of his neck, the veritcal line. Two brighterpixels in an even line down the length of the neck are to their right accompanied by a much darker and abrupt shade, wich creates, at least to me (perhaps Im trying too hard to find something to crit, forgive me if I'm being too nitpicky) a bevel effect, like this ---__ where the higher, left lines are is the edge of the neck and the lower lines are the darkness to their right, when it is infact meant to be like this I believe__---.
/babble.
Do more.