Here's a cheap way to try it. Go to your local dollar store or whatever and buy a nice blue foil wrapping paper. The foil will not be ruined by the water around the tank if it splashes during a water change or anything and it should cost less that five dollars. As opposed to 3-4 dollars a foot for the background bought a your LFS. If you are not sure if it's what you want it is a really cheap way to try it anyway.
This is what I have on my 55gal tank and it looks great (and it cost me $1.20 for the entire tank and I still had enough for my sister's 10 gal). You can also change it up fairly eaisly with the black you already have or buy a nice sliver foil paper to create a mirrored background that also looks nice. By buying the wrapping paper you can also change it for the seasons (christmas, easter etc.) It may sound kinda tacky but trust me you can get very creative when walking down the gift wrap aisle at your favorite store
By buying the wrapping paper you can also change it for the seasons (christmas, easter etc.) It may sound kinda tacky but trust me you can get very creative when walking down the gift wrap aisle at your favorite store.