I know it's against every rule but I also love flat black walls in small rooms. I had my (TINY) art studio painted flat black at my prior house and I LOVED it. No reflections, no color changes, and even though everyone says it makes rooms feel small, it actually made the room feel HUGE because the walls essentially vanished. Repainting the room before I moved was horrible, though, so I haven't done black walls again in this house because I know we won't stay here long enough to make the effort worthwhile.