Not counting the upcoming packs yet, and I'm only suggesting 'new' stuff.

Flag Run:

Possible levels: Action Basement v2, The Crosscut, Halls of Judgment

Battle:

Panic!!, The Warden Woods, Intercity Grudge Match(if it gets finished?) Central Shaft, The Frozen Throne

CTF:

Botanizer, Undulation/Cross Circuit, Earth, Center of the Universe, Evening Shades, Sunken Realm

Upcoming packs like Impressions E and New Ages III have some Bash-material as well. Hopefully they'll be released before the Bash(I'm almost certain that they will)

Levels from New Ages III: Echo Isle, Siberia, Land of Kaamos, Northscar Needle

Levels from Impressions E: Scrap Brain, Mixxed Up, Colourful Compact

Those are just suggestions, but I'm pretty sure some of these are good for the Bash.