It depends whether you prefer lighter shades or do not mind more color. For an off-white or pastel, try a pink or rosy tone: on the color strips, the dark shade in the same group will be a mahogany color. For more color, try a sage green that picks up the earthiness of the trim and the gray.
A light coffee colour will work well, perhaps with a feature wall in terracotta on one side. If feeling more daring, a deep red, almost maroon, will give a fantastically modern feeling to the room, complimenting both the trim and the carpet. It will also make the room look warmer and more sophisticated.
Give the walls a splash of bright color! There are limitless choices. Something warm and light would be good - such as yellow, peachy rose or a warm sea blue.