I love your stuff, and I would suggest doing a buy 3 get 1 free or some such.... I think 50% or BOGO sounds too desperate & mankes poeple wonder about what's wrong with your stuff. Most poeple I see doing a giveaway like this generally do a buy 2 get 1, buy 10 get 1, etc.
P.S. i would also show your custom pet cutouts in a frame, to define taht the merchandise isn;t a card but a portrait. The first thing I thought, after seeing your avitar & then seeing the pricve of the first thing was OMG - that miuch for a card!?!!!