I dunno enough about realism to really critique you, but I can say I recognized who it was just from the preview. xD Good job with that~
But I guess if you had to fix something, his face is a little wide. Like, the space below his mouth/chin should be a little thinner. His left eye (right eye from the picture) looks off-center but that might be from the scan since you said it's not noticable irl.
That's all I can think of, hope it helps. :'D