What do you want? (remember I am shit at making maps, I'm sure you remember aop_mayhem_2k7 (it's on the aop server if you don't), round times of 10 seconds)
Not going to do any fancy texturing, so will be in the same style as mayhem_2k7.
Idea 1
I'm thinking a square map. spawn points are opposite each other on different sides. In the middle will be an underground tunnel type thing. There will be three bridges, 2 small ones on the side and a big one in the middle. All 3 bridges will have obstacles to hide behind. There will be 4 ramps to the underground bit, 2 from each side, between the bridges.
Not sure whether the underground should be exposed from the bridges or not. If not, should there be some tough glass so you can spot possible campers easily in the tunnel?

Idea 2
Similar to idea 1 (square map, spawn points etc), but have a large openish area in the middle of the map with small bridges connecting in to it from the spawn points with no tunnel (or possible mini tunnels to try and ambush the opponents)

In the images, the darker colours are higher up, lighter colours are lower down.