Try using a uniform pale colour on walls and ceiling, and a toning shade on the floor. If it's a modern room, transparent tables and/or chairs will work wonders. If not, avoid any big 'statement' pieces of furniture and keep the decor as simple as possible. Mirrors will work well, and will bounce light around - you need to maximise the amount of light in the room, to add to the feeling of space. Ferny plants, if you have the right conditions for them, will help make the room feel light and airy. Avoid big, architectural plants as they will make the room close in.