Take an existing and well known deathmatch level (although I forget its name) from the /idgames archive, mess around with its textures a bit, add an ugly looking skybox and then put some Quake2 models into the skybox.
OK, not the prettiest screenshots on the planet, but the Viper ships flying through the skybox look good.
Of course, they look much better moving. Don't believe me?
http://www.youtube.com/watch?v=mzdml88eY-E
OK, so Youtube messes up the quality, but you get the idea,
