I would build upon Chillingworth's and Hester's physiognomies. As the novel progresses and Chillingworth becomes more and more bound to his obsession in first seeking out the father of Pearl and then punishing him, we see him follow a physical trajectory as well as a moral one. When Dimmesdale and Chillingworth move in together, there is a blackness associated with Chillingworth that people attribute to his experiments, but that symbolically represents his obsession. Then as Hester seeks him out to tell him she will no longer keep his secret, we see that not only does he have the blackness to his complexion, but that he has become entirely stooped over, and as he continues gathering his herbs, he scurries along the ground, his beard almost touching it, almost like an animal, representing his complete moral descent into obsession.
Hester's appearance is likewise important. When Hester first emerges from the prison door, Hawthorne dwells upon her beauty, which, juxtaposed to that of the goodwives, indicates her sympathetic nature, but it also establishes her as a nonconformist. Throughout the novel, Hawthorne provides us with little questions and insights that show us that Hester is not given to believe the same things as the rest of the Boston community, but that she keeps these feelings hidden, and won't even confess them to herself. When Hester is not true to herself and these beliefs, and allows the scarlet letter to be her identity, she fades into the background and loses an element of her beauty. But when she seeks out Dimmesdale, sheds the letter, and embraces the passionate woman she really is, we see her beauty return immediately, only to be hidden again once Pearl demands she put back on the oppressive symbol.