You're dealing with a tough face as a pallette. Some time ago, someone was talking about it. The two sides of he face don't match. The left side is not a mirror image of the right. So gettuing it to look good will be tougher tahn a really good sculpt.
Someone else was asking about a 120mm face he was painting. Some of what I said to him appiles here.
You might want to add highlights along the ridge of the nose, the chin, the upper edge of the lip and on the two folds of skin under the nose. Carry the nose ridge highlight to the upper edges of the nostril flare. Add highlight to the central part of the ear. Also increase the cheek highlight and bring it down along the outer edge of the frown line. Also along the top of the eyelid. Add a highlight on the adam's apple.
Add some shadows to the hollow of the cheeks, in the frown line, in the cleft of the chin, above the eyelid, in the space between the raised flesh under the nose, under the neck, along the hairline, in the hollows of the ears and behind the ears. Add shadows below the adam's apple .