You really can't go wrong with paper lanterns when trying a quick decorating job. They always add a whimsical flavor of fun. They are great for kid's rooms, especially, or for any room that just needs some spice. Or, if you have a fun pattern in a room and want to draw out the the colors with some solids, lanterns are a good idea. My favorite place to use them is in apartments where you can't paint the walls. If you can't add interest to the walls, try adding it to the ceiling.
Martha has a great tutorial on how to make your own tissue pom poms.