Due to the reasoning of the server becoming 24/7 Minecraft and the incredibly success dependant upon this, the map isn't going to be changed from ttt_minecraft_b5, nor are new maps going to be added, we also have our own Map Voting addon here at ZARP, ShoutVote, made by ChuteUK, Community Owner (Check it out:
www.gmodstore.com/market/view/86)
If a second TTT server eventually happens, then this will likely have a wide map pool, however this does not look likely at the moment, as we have other areas of the Pointshop to focus on without also having to worry about introducing any new servers.