Here are some ideas:
Use pretty and interesting wrapping paper and frame it. Instant art! Plus, you can change it whenever the mood strikes you.
Vinyl Wall stickers are easy to apply and are removable.
Hang a rug on the wall
Make a wall of your kid's artwork
Tatouage is easy to apply. It is applied by transferring the art with pressure and comes in many styles
Hang plates on a wall
Add texture and dimension with wall art made from coffee filters
Enlarge family photos
Hang an interesting quilt
Frame maps to add interest to a space
Make wall art with paint chips from the hardware store