Hang up a large piece of artwork over the wall you want to hide. Artwork may not look appropriate in certain rooms depending on the theme and purpose of the room. For instance, a large movie poster might look strange in the kitchen.
Place furniture in front of the wall or curtains. In a bedroom, put a tall, wide dresser against the wall. In the living room, try a bookcase or two.
Hang a sheet of fabric over the wall or window. Most craft stores will cut a sheet of fabric to match your wall's measurements. A blanket or attractive tapestry works well, too.
Cover the ugly walls with new wallpaper. If you're renting, ask your landlord's permission.