Man this piece is phenomenal, very nice use of shading anatomy and line weight!
Only thing I note is the eyes are crossed, both contracted inwards, could be strabismus or if he's looking at a very close up object like a fly passing by his face - if done on purpose, you definitely got it right I think (maybe the figure's left eye would have the highlight more towards our right as the eye would be rotated to our left) - if not, then I would suggest adjusting the direction of the eyes and taking into consideration the light, slight adjustment of the corneal highlight so both eyes have the highlight in the same spot (different spots for the highlights is telltale sign of strabismus if the lightsource is coming from the front or similar arrangement)
