Wrap a piece of cardboard in fabric and put at back of bookcase instead of painting or wallpaper. Could change out as often as you want -- built-ins!#Repin By:Pinterest++ for iPad#
Also on these boards
DIY: Painting Fabric Chairs - lots of information on how to paint on fabric. This is a brilliant way to change the color of a chair, but at a fraction of the cost of having it upholstered.
Bookcase on its side and adding legs makes a whole new piece of furniture.