Great job on your back grounds! I have made some for my cichlid tank, but I have not made one for my BP tank. I have simply spray painted the sides and back black on my 30g for a back ground. I first painted my salt water tank to bring out the colors, but ended up really liking the look.

Just take a look at the African Savannah for some inspiration. Looks like you can build, so I look forward to seeing your new project! Have you thought about making a step by step for the DIY section of BP.net?