I imagine the best kind of theme would be somewhere between chiptune and 90s .mod tunes (maybe both?) which would fit the old-school styling of CC2.
Then there's another issue: should we use only songs that are public domain/royalty-free/by unknown composers/made specifically for this level pack, or should we feel free to throw in whatever tunes we want (as long as they do not say "do not use except in the appropriate context") and then give the composers credit? The latter option seems legally immoral, but if a partial rip I made of Super Meat Boy's soundtrack is allowed on the forums, something similar might be allowed in a community level pack.
Then there's another issue: should we use only songs that are public domain/royalty-free/by unknown composers/made specifically for this level pack, or should we feel free to throw in whatever tunes we want (as long as they do not say "do not use except in the appropriate context") and then give the composers credit? The latter option seems legally immoral, but if a partial rip I made of Super Meat Boy's soundtrack is allowed on the forums, something similar might be allowed in a community level pack.