Using light colored fabrics and upholstery are a nice and soft contrast to the dark walls. They also reflect the light that's coming in from the windows which keeps the room from not having any depth.
Consider sheen and patina too. Metallic gold bookcases reflect light. Also consider the "visual weight" of your furnishings. The desk, while large - has minimal visual weight because it is clear. A thick blocky wood desk would add a lot of visual weight to the room.
Here is another example of using light (in both weight and color) textiles, and reflective surfaces. Getting a semi-gloss or gloss paint will reflect light.
I actually think that small spaces done in dark colors feel extremely rich. The herringbone floors, moulding, and large window don't hurt either!