Your setup would look much better with a black background. Without it, the black center overflow took center stage of your display. Once you put in the black background, the center overflow box would blend into the background and your live rocks and fish would pop out like a live picture. Since your tank is already setup against the wall, it would be a challenge to paint the back of it. I would just buy a piece of black aquarium background sheet from an online store for your tank size and tape it to the back of the tank.