Big thanks to Frank Tzeng for his great tutorials and he is my mentor…
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Your C&C welcome…
I think you’ve done a great job at anatomical forms and facial details. I’d just like to see more shots of his head all over.
One thing that bothered me a bit in Frank’s tutorial was that he didn’t pay enough attention to the convex back part of the ear, which is formed by the concave concha area of the ear from the side view. Even though his portrait was just for rendering it out from the front view, I usually respect every area in the anatomy, even areas you can’t see in the final result, just for the sake of learning the anatomy.
As your guy is a bald one, there are more reasons to get the ear right, you know. 
As far as I can tell, you seem to be doing okay from these shot you’ve taken.
Overall, keep up the good work.
EDIT: Is he your personal mentor, guiding you to become a character artist? So, he keeps a contact with you regularly? If so, that’s cool. He’s one of my biggest inspirations too.