We did a little two helicopter display to music in Redhill a few years back. Great fun to put together, not sure what the audience thought.
Some of the moves were the ferris wheel where the helicopters circle over each other whilst facing the audience, the planetary gear, where they rotate around a circle whilst spinning on their axes, the challenge where the helicopters depart backwards then reverse to pass while banked, the pistons where they go up and down in opposition, and the falling leaves where they descend whilst spinning.
I think the two (or more) helicopter show is the best way to display helis, as you say it's rather dull just doing one (unless it's a Bolkow !)