My wife tells me that if I hit a bad note, my mustache twitches. I don't "make faces" when I play, but a bum note will make me grimace, and the mustache accentuates that. Which sucks! (Actually, it's not so bad, since no one can ever hear the keyboards anyway. People just think I'm making faces.)
I love the "random eye contact" thing. Nothing psyches up a fan more than when you look them right in the eye while you're playing. You're playing to them! I spend at least half my time on stage gazing into the audience and staring down random people. If they see me and we connect, I smile, they smile, and I move on.
(The other half of the time is spent checking out random babes. They're always gazing at the singer or guitarist, though, so no eye contact is ever made. That's okay; I can stare longer at the hot ones without fear of getting caught.)