I did this in my apartment in college and I loved the feeling it have the room. Use curtains instead of wallpaper. Great for apartment living. Maybe use a rod the same color as the wall or the curtains. Hang as high as possible.
I would love a bedroom with French doors that open to a little private garden space. Once our lives regulate a little, we have plans to turn our master bedroom's double windows into French doors that lead into the back yard.
This idea can be useful in many ways. Define specific areas in your space such as a reading nook or eating area with just a portion of he wall painted. It's also just a great way of introducing some colour when you don't want to paint an entire room.