thin the hair, it seems too full. go back and redo the lips, the shadow will do a slight break before the lipline. in your picture there is no break, making it look like you put a sticker of lips on the picture. there is no 3d feel to it.
eyes spaced further apart. (rule is one eye width between the two)
and reshape and slightly shorten the nose... or extend the jaw and shift the lips down.
the mouth being agape is going to change your entire face shape, so you must take that into consideration.
and his left hand needs a little work.
what i do like about the picture is the shading effects of the skin and clothing, curtains and other objects. this will of course help you if you apply it to the lips.
just practice on facial expressions and anatomy of the skull and you'll be set.