Wallpaper Lining
If you found wallpaper you're in love with but it's not removable, get this easy-to-peel-off wallpaper lining, and cushion it between your wall and paper. Not only will it make your design rental-friendly, but it will also help the wallpaper go on smoothly and with less hassle. 

Brewster 92599 Lining Paper Prepasted Lining Paper Wallpaper, $25, Amazon