http://www.bungie.net/stats/Halo3/FileShare.aspx?gamertag=ssshakedown
http://www.forgehub.com/home/index.php?topic=742.0 is the original thread. Everything is explained there.
It's the same map (so all the screenshots will be relevant), but I tweaked a few things.

The man cannons now work 100% of the time
The energy sword is replaced with a gravity hammer
I added 4 firebomb grenades (1 on each side, and 2 in the sniper tower), to make the 'Hog easier to kill
I reduced the shotgun clips, so they start with 6 shots rather than 12
I added more spawn points to prevent spawn-killing and emergency spawns that leave you trapped
The crane arm hanging above one side has been booby trapped to prevent unfairness

Oh, and the name doesn't suck anymore.
In my opinion. ;D

Screenshots, now in this post.
FROM VERSION 1! The map has been modified since then, but the main architectural points are the same.
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/Bases.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/BasesCloser.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/BasesCloser2.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/Back.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/TopView.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/ShotgunSpawn.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/ManCannon.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/Base.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/15561381-Full.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/HogAndFlamethrower.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/SniperBox.jpg
[img width=800 height=600]http://i256.photobucket.com/albums/hh194/ssshakedown-/Halo%203%20Map%20Screenshots/TopView2.jpg