I was thinking maybe lights, or fabric.
Since it has such a unique design, too much will take away from that. My daughter has an old 4 poster canopy bed and we just hung fabric from the rail that runs parallel to the headboard. WE drapped a LONG, white tulle, curtain over the rail so it hangs down behind the headboard. You can still see the wall color thru it, but it adds just enough detail, interest, and softness w/out taking away from the beauty of the bed itself. You could also use beads in addition to or in place of drapping fabric.
You could definitely use lights. Maybe some silk flowers, ribbon, tulle. I personally would probably put white twinkly lights, some assorted silk flowers a thick ribbon to compliment the flowers and a thin gold ribbon wrapped loosely around around it.
