Well, if there has to be some "not so popular"-levels, I would recommend:

-Medieval Skycrapers(yet again)
-Tunnel Torment
-Marshland of Evil(which could have been played at this season as well but none of the clans chose it)
-Jungle's Edge(same thing)
-Just Got Carrot Away(j/k)
-Waterfall Caves
-Divide and Conquer(Some blur's level, which he used for some offic. vs comp.-event)
-This level is untitled(=Evilmike's snow level)
-SPACE ISLAND LEVEL WITH ISLANDS
-African Lowlands(A new level by Snooze, but I'm not 100% sure if it's playable)
-Superconductor CTF(Might be too small, although Semi was played at this season as well, although it's just a little bigger than Super.)
-And if I can get my level finished before jj2wc 2, which is going to be quite large, you can choose that as a level as well.
-Ragnarok's stronghold
-Apocalyptic Afterworld
-Fright Night CTF
-Angelic Warfare

And a ton of other good levels to choose.
There is already 15 choices and I think that at least one of those should be chosen to the next season. And don't count the little joke I added there.
I think bbswing is a little too small for 3vs3.

It might be a little early to think about the levels already but because I was so bored, I decided to make a little list of levels what could be played for example.

And a question: Will [si] play in the next jj2wc?