A thin piece of Cellophane of any size sticks to any surface wether it's cealings, floors or walls; even to your computer screens. With any possible surface, imagine you can easily transport designed art with no trace left behind. No more nails, glass, frames, holes, etc. - just Cellophane hanging around the house. How about a two sided cellophane sign saying "Occupied" and "Unoccupied" for the bathroom door. Unlike all other materials, Cellophane never looses it's power to stick.
Reward: Try opening a cigarette pack and stick the Cellophane wrapping to a wood door. It Sticks!