If you are EXTREMELY bothered by using this stamp on a post card, I would say to put a regular 45 cent stamp (they have pretty roses and other wedding related themes to choose from) because it's still not as expensive as the custom design.
To be honest, I'd rather save those few extra cents to put towards something else. Although I didn't like the look of them, my mama graciously and helpfully addressed, stamped, and mailed all the post cards and I didn't have to even look at the stamps. It helped to have her take care of it so I didn't cave in during a wedding mini meltdown and make a rush order for the custom stamps. Thanks mom!