thewickedgirl : might want to check out flash techniques...think currently only the 580EX series for canon able to have Stroboscopic flash // Multi Mode allowing you to have that multi exposure look.
I think multi-exposure is mostly used for landscape, and flash is not very useful in this case. However, 580EX II is a dedicated flash, should have if you like portrait photo. Another option is Nissin 866pro, much cheaper, similar function, though noisier.