I figured that something like this might come in handy. I made a map called td_virtualsets
download here. It's got plenty o green area (green screen), and I've included at no additional cost: Red, Blue, White, and Black sets as well.
Also included are red and blue spawns protected (marginally) from spawn camping sentries (in case you want to get an enemy in the shot). There's plenty of metal and health packs and a purty sky.
If you want any kind of prop or decal/texture put on anything, let me know. Its pretty easy.