It's not just the shaved head. It's his attitude and his "deadpan" speaking style (yes, I know it's just reading, work with me here). For me it comes by way of his character Riddick from the Pitch Black movies, and what little I know of the FF movies.
As for Jessie Williams, I made the connection more off of his attitude than his actual look. I only know Williams from when my then-girlfriend got me into Grey's Anatomy. Now that you mention it, I can see the resemblance, but nothing in his mannerisms made me think of that character.
Shoot, I think I would have connected the MC to Michael Clarke Duncan's character John Coffey in Green Mile before thinking of Jackson Avery.