I never noticed it until I saw this drawing, but the second one, where he looses his head from 'Terror' kind of reminds me of some kind of super villain - a robot with a glass dome over his brain. I just can't seem to recall who it's reminding me of.
When i did this sketch card commission the person wahnted two cards and just the head. I usually don't just do "HeadShots" - not a fan of them. But that's what he wanted. The only character I can think of is the one from DC Comics - The Brain from Tenn Titans???