I promised maps earlier, and the two maps on Halo 3 that I have made are now on my fileshare.
Fort (very unique name, I know) is good for 1 bomb assault, and capture the flag, although it could also be used for Infection (it was never tested with the Infection gametype, so hopefully the attackers are the zombies). It's asymmetrical, with a large, heavily fortified defender's base and a small, but shielded, attacker's starting point from which to coordinate their assault.
Sandbox Bash is symmetrical, though each team's base is drastically different in layout and makeup. Both teams have the same weapon setup (I think I stuck almost every weapon available in the armories), as well as equipment. The blue base is up in the skybox, and the red base is on the ground floor, and it is impossible to get outside of either base, except through teleporters. The teleporters lead to the crypt, which is devoid of any weapons or spawn points. It is the most strategic point of the map, however, for it provides the only link between the two bases, and also contains the hills in King of the Hill. Bombs spawn in each base's armory, and the plant point is in the same location on the opposite team's base.
Sandbox Bash is far from my best map, and needs to be revised for two reasons:
1) all of a team's spawn points are in one room, making spawn killing a very real and annoying possibility.
2) I believe that there is a missing hill, lost somewhere on the map. One is in each corner of the crypt, and only 3 remain in the shop to be placed. If anyone could find that hill and tell me where it is, I'd be grateful.