a skeleton, laying down and hollow in certain areas.
would make for an epic tdm that would require little actual building.
or what would be even cooler is having it like this (probably wouldnt work but i dont care)
have it be a graveyard where you spawn, and at one of the graves have a hand sticking out that you can walk into and down to get to a catacomb of coffins and worm tunnels, so that it would be like insanely epic team base deathmatch.