HAH!! SUCH PERFECT TIMING as I've been considering this Very thing tonight then I saw this note!
Initial & PRIME option I would LOVE to work with are transparent decals, so we can design 'viewables' ;) for smaller windows in homes, vehicles, lockers, computers, etc, that is removable. (Ex. I'm thinking about the 'stick figure families', ocean critters, etc I see in vehicle back windows.)
I've been trying to see if I can make some with products currently available, but either I'm blind or daft, as I'm just 'not seein'' how it could be done.
Also love others ideas re: metallics and die-cuts.
Thanks for asking!