It's going to be nice when the sagitteria fills in! Try some plants attached to the driftwood (moss, ferns, anubias) to fill in the picture. I'd get a background too. The tank looks like it's filling in nicely.
a background finishs the tank get a natural see one with plants on or a blue black ground. I can get one from my LFS its light at the top and gets dark as it goes down.