You can also use this feature as a kind of rough-and-tumble collage or composition tool. Open an image, create a scene, and then plop-render or ray-spray-render parts of it. Make sure to do ray-spray-render while in Render View Mode, not Wireframe View Mode, otherwise you'll lose the rayspray pixels. Save the image, and repeat with more scenes. Voila, instant cheesy collage!