I'm thinking this might be an adorable keepsake: everyone in the bridal party/all the immediate family girls kiss a piece of paper to mount and frame in a funky old frame. I'd have them sign their name too.
The bride and groom requested that their guests respond to the invitations with a piece of fabric- any fabric- and was incorporated into a quilt for the newlyweds to have for the rest of their lives. What? Love!