Another idea I had for a map (inspired by those giant house/rooms UT2k3 maps) would be a large open-sky crater, with giant corpses modelled after the UT2k4 character models.
If it's a ONS map, each base could be inside two corpses, with the powercore being, for example in the skull of a giant robot model, or in a hole over where the heart would be if the model is non-robotic. Power nodes could be located inside giant versions of UT2k4 weapons.
At least one of the giant corpses should not be totally decomposed, and it should be possible for the players to go end-to-end through a biologically-correct digestive tract, with a puddle of reddish brown liquid at the nether end...
Some giant skulls and other giant body parts could also be littered along the crater floor.