winkles around the eyes, mouth, chin, nose, forehead. areas that deform a lot over time. Changing the pore structure on each element will help a ton as well (the pores on your nose look different than the pores on your cheeks, etc.) Having a quality spec map can make all the difference. The presentation of the underlying colors will help a ton as well. Yellows, blues and reds in every face. He needs much more definition at the nostrils as well as the bridge of his nose. An AO pass always helps the presentation of any piece. Dark stubble (5 o’clock shadow) around the neck and a little up on the cheeks. Longer eye lashes. Thickening up the lobes of the ears. A darker background will help a ton as well (a flat white is always boring…well, usually). He also doesn’t come across to me as the type of person that looks up like that. He seems more one that would look at his feet while walking. A slightly lazy eye adds character…as well as relaxed eyelid muscles on one eye adds a TON of character in my opinion (forest whiticer…oh however you spell that).
Adding a texture/shader/material to the jacket to give it an actual material would help this piece.
I hope some of this helps.