Depth of field in macro photography is so narrow that the background rarely turns into unwanted clutter. The clinical stark black you see so often in macro shots comes from the need of stopping down the lens - for maximum depth of field - to the point that you need a flash. With the shallow light from a ringflash or lateral light from a single-flash bracket, too little light reaches the background, resulting in that clinical black. Easier than carrying a series of backgrounds might be a small flash unit with a built-in slave, so you can choose what you want to illuminate as background and how much.