For odd time sigs, as mentioned most 6/8 and 12/8 feels can be done well in 4/4. And most 9/8 works in 3/4.

But of course there are exceptions to that, and many other time signatures.
We have support for lots of odd time signatures. This is present in Styles disk #38.
http://www.pgmusic.com/styles38.htm

<< I would like to create backing tracks in 9/8 but I want the emphasis to be 2-2-2-3.
For example, the style "98_4_5.STY 9/8 Meter style" likely has the 9-8 feel that you are looking for 2-2-2-3
http://64.40.109.185/pgmusic/audio/sty38/high/98_4_5.wma

Note that the notation for these styles isn't 9/8, so if correct notation is a "must have", then this styles disk won't help. But if you want to play all kinds of odd-time signatures in BB, including things like 19/16 etc., then you should explore the styles on this disk.

Have Fun!
Peter Gannon
PG Music Inc.