Interesting question, I've wondered about dancing with snakes myself. I keep many reptiles (including corns snakes and children's pythons) and I'm not sure if I'd want to dance with them for fear of stressing them. Granted I've have done a couple of spins with my larger corns when taking them to thier feeding tub heehee.
Blood Pythons, if I recall correctly, can be somewhat docile if handled regulary from a hatchling. Though thier husbandry requirements would make them a more intermediate-level snake. They can also get to 7 feet, and 40 pounds, and if the snake were to bite, they'd pack a punch I don't think anyone would be able to take gracefully onstage
I second the motion of a Boa or Ball Python, very mellow in general.
S1dur1-I love Bullsnakes, they have character, 'expressive' faces!