Those fine fellows in Total Annihilation clan kindly sent me a copy of their own private map, which looks to me like the work of Sharpknux; the colours in some parts are only seen in his maps!
I have only explored it on my own, and I may well have missed bits, but this seems to be at least five or six arenas in one - all a little simplified, to keep the total size of the download within reason I expect. There is a "Forts of Independence" style area; the one where I took this screenshot is "Forest" trimmed down (note the hummock to hide in just above my pistol's sight) - and on the left is access to a desolate, rocky area, while on its roof are a number of strange teleporter cubes...or are some of them meant to be traps?
To the right we can see an area of yellow spires - and beyond that is a large low-gravity arena, where you can jump from one ledge or column-top to another, picking up weapons etc as you go... and I may well have missed some doors, passageways or teleporters, of course!
So, great for training and exploring, though for fighting it would take a long time to get back to the battle if you got respawned back over in low-gravity. Personally, if I was joining a clan to get their exclusive map, I think I would go for CD, where the map is a nice friendly size, and you get a website too, with e-mail addresses for your fellow members, the rules and guidelines set out neatly, and even a "hidden page" or two, password-protected... but I may not be entirely neutral on the subject...