This is a big team battle map (recommended 8 players on each team) completely made by me but some ideas come from one of my friends: xXxJeremy71xXx
It has been tested seriously once in a custom game with 16 players, as it is hard to find people willing to help test, but the game and feedback turned out fairly great.

The bridge which resembles the bridge in the map from Halo 3 ''Narrows'' marks the middle of the map. The top floor is mostly used by land vehicles found on the map (ghosts, mongeese, warthogs) the bottom floor is more suitable for infantry. A rocket launcher can be found in the middle on a floating platform on the bottom floor. The bridge is connected to a higher platform
accessible from the middle of the top floor of the bridge or by two light man cannons found on each teams' side of the map. On this platform a spartan laser can be found. The team's bases are symectrical, with many entrances; from the obvious to the more hidden. Each base has a sniper rifle on the top floor, a shotgun, a banshee and shade turret on the roof, two mongeese, a warthog, a ghost and other items such as DMRs and health stations. Each team has access to a man cannon which sends them past the chasm and onto enemy territory. These man cannon stations are not symectrical for both teams. A grenade launcher and plasma grenades can be found here. This map has many respawn points scattered around each teams base making 'spawn trapping' very unlikely. Feedback and tips are very appreciated.

Pictures of the map:

This is the bridge, probably the highlight of the map, as you can see, the top is mostly where vehicles pass by and the bottom part is more infantry-friendly, to the right is the higher platform accessible by the ramp on the bridge, or by the light man cannons. At the top of the sniper's nest is the spartan laser's spawn.

The red base. As you can see they are two obvious entry points and the other... not so much... :P Up the left entry way is the sniper tower and access to the roof; where the shade turret and banshee are located. The right leads to the shotgun spawn. (note the blue base is exactly the same as the red base except for some small details due to non deleteable objects and the way the terrain is made.)

Another view of the bridge, with the blue base in the far back.

The back of the blue base, and the rest of the map in the background. As you can see there is much room for land vehicles to move around while having a few rocks to hide behind.

This is the sniper rifle spawn, turn around 180 degrees and your on red team's base's roof, where the banshee and shade turret are found. Very nice clear view of the whole map for the best sniping experience.

The back of red team's base, also where the initial spawn and mongeese are. The glass box room is where the flag, (during CTF) the planting zone (during assault) and stockpile (during stockpile) are. There's some nice space for vehicles to move around and easy to drop off passengers to enter the back of the base. (note that blue team's initial spawn is in the exact same place behind their base)

This is the bottom part of the bridge, the middle floating platform is home to the rocket launcher's spawn. (note that the 2x2 flats to make the oval have been replaced with diagonal bridges; as suggested by MCGreen24)

This is the platform beside the bridge, infantry friendly, accessible by the bridge and by two light man cannons. The sniper nest is where the spartan laser spawns.

Blue team's man cannon, a short stroll from the base, and BAM! You're flying through the air until you find yourself in enemy territory. A little walk up the entrance a grenade launcher and plasma grenades are at your disposal.

Red team's man cannon, a little different than blue team's but still provides the same service.

A view from the ghost's spawn of red team's base again.

Again, your feedback and tips are very much appreciated. My goal is for this map to make it on the matchmaking playlist in the big team battle section.

Also I am looking for people to help test a few games out to see how it flows. So if you would like to lend a hand add my gamertag to your friends list: SAMULICIOUS

Oh, and one last thing: I've noticed that if you jump onto the man cannon instead of walking onto it, you miss the landing zone short and smack your head on it or miss it completely...Any tips on how to keep players from jumping onto it? I was thinking a roof might do the trick but I am extremely low on budget.