I own the following accessory bags: Pochette Cosmetique, Poche Toilette 15, Pochette Acessorires, and Antigua Pochette Plate PM.
I think the Antigua Pochette Plate PM or GM would hold the most if you carry a lot of make-up since it's flat and rectangular in shape, however, since it's made entirely of cloth, it could get messy if your make-up spills.
Otherwise, maybe go for the Mono Poche Toilette 19 because that would also hold a lot of make-up - it's also rectangular in shape but it's not flat and since it's mad of Mono material, the inside can be wiped with a cloth since it's the inside of the Mono canval (not cloth lined).
Ironically, I don't use any of my accessory bags for make-up, but I use them to hold all sorts of other things - Palm PDA, credit cards, coupons, tissues, tweezers, lotion, etc.
Good luck!