you could make the arena look like a trampoline
Or you could design it to look like large and small trampolines next to each other.
You'd have the hard outsides of each individual trampoline which didn't bounce you.
And if you made large trampolines, they would bounce you higher.
So, as you move across the map, people would bounce at different heights providing more variety to the map.
Atleast that is one way of making it more unique, while not relying super-heavily on lots of excess obstacles
Although I still suggest you try to put somethings in if you can.
Why not having a tall ceiling and have walkways and things suspended from the ceiling, and you can sometimes bounce up to them?