Plain white to match the trim would be fine, too.

You need something bright in here. How about a nice bright rug with light grey geometric shapes.

I would say a cream or a light warm tone - not the same color as the walls, but something similar perhaps. Skip the pattern on the curtains - you have lots of good pattern going on with the pillows and you won't want your drapes competing with them.

Patterned drapes a good idea. Large rug. Larger coffee table, one now is useless for some people. Square or movable grouping. PB End tables with lamps. Pillows are wrong scale, too big, also need texture not just pattern. Different sizes. Smallish swivel chair, texture or subtle pattern, to the left of the fireplace.

Wow, lots of good suggestions. Makes my search a bit easier.