Cut the hems off a flat bedsheet that has a decorative pattern you like. Soak the sheet in full-strength liquid starch. The starch will act as a natural adhesive. Smooth the sheet over the wall behind the bed, starting at the ceiling line and working down. Use a squeegee to smooth out wrinkles. When you want to redecorate, you can easily pull down the sheet; the original wall finish will only need wiping down to be restored.