To add visual interest to a small space I emphasize my walls by creating diverse galleries and using different painting techniques. As for the furniture I create flow by using light hued fabrics for my large pieces such as my sofa and then add contrast with dark theme inspired accent pieces to keep the room grounded.
If you are using your sofa for a room divider it is very imperative that the fabric is light and airy, remember it is in the center of the space. A dark sofa would make the room feel cut off and dreary.
I added feminine flares to my space with a scroll pattern rug, embroidered feather down pillows, crystal accents (the lamp and pastry tier in the back corner) and a leopard accent chair. To entice my guests and make them feel more at home I like to have several arrangements (living or perceivably living things make a space feel less cold), candles for aroma, and a sign of dining (the sesame rolls plated in the serving basket).
The large diagonal stripe draws your eyes upward making the room appear larger. Most people stray from using black in small spaces but if you add black as a focal point while keeping the other accents light and flowing it can do wonders for expanding your small space.