I had natural colored gravel in my RCS tank. When I switched to black sand their color improved immensely.
In my old 75g (oscar & sev) I found an awesome background that looked like rocks, really added a lot to the tank.
I had a dark tank once that I used aluminum foil for the background.
I also did a true Asian tank that I used brown paper bag for the background.
I personally wouldn't paint in case I changed my mind Lots of different things you could do though depending on what you like and what you'd like the tank to be.
In my old 75g (oscar & sev) I found an awesome background that looked like rocks, really added a lot to the tank.
I had a dark tank once that I used aluminum foil for the background.
I also did a true Asian tank that I used brown paper bag for the background.
I personally wouldn't paint in case I changed my mind Lots of different things you could do though depending on what you like and what you'd like the tank to be.