Read more on Window Treatments
Try hanging your curtains well above the actual window height and beyond the width of the window. (Take care not to make the window appear to large for the size room you are working with.)
Hang a rod and some curtains on a blank wall, you can add a mirror in place of a window.Decorative Screens
Screens are fantastic for adding interest to a room and filling a corner. They come in many different sizes and styles.Foliage
Use a tall silk tree, and string some clear lights on it to add soft accent lighting to your room.
Floral swags over a window, door, or mirror will add color.Shelving
Mount shelves and place plants or a small grouping of "like" collectibles. Try resting a piece of artwork on a shelf.Artwork & Photos
A nice piece of artwork will always add interest to a room. When hanging one piece, make sure it is properly sized for the wall you are hanging it on, and be careful not to hang it to high on the wall. Group photos and evenly space them.Fabrics
Use light weight fabrics. Tack and pleat the fabrics right where the ceiling meets the wall. You can run them the length of one wall or use this treatment to create a focal point. I have even gone so far as to hang decorative area rugs on walls!
Lighting in a room is very important. The use of different types of lighting will change the way you see and feel in your room.
Accent lighting will add some drama, and highlight areas of a room.
Incandescent lighting will add more warmth. The three types of lighting are, general, task, and accent.