The DAZ 3D environments use this sort of prop, a simple square with texture and transmap, for a lot of the grasses and small plants. I noticed the woodland playsets didn't have any branches coming down from above, and knocked this up from a photo taken in the garden. These images will work, but the JPEG compressing may be a little high. The DAZ textures usually have a black background, rather than white. Anyway, if you look at the set in a wireframe mode, you'll see that the Cyclorama has a couple of sections which use this trick, for things such as trees or rocks on the beach. And it's easy to make and add your own simple props, to ass a bit of depth to the background.