This is my first post I am making on this forum , myself also being new to Aquascaping ... or new to everything itself. I like Keithgh idea on black and or soft marine blue. Vinyl idea is good which I made just try. You can also try with bristol board just for a Dollar at local dollar store get a couple and place it in the back to see how it might look then from there move on to the getting a vinyl/ tank background or even print your own out which some people have done . I like the tank its coming along great , your time , patience and hard work have not gone to waste.