Have you tried "doubling up" on your renders? Render the background without figures. Save the camera and lights Apply that render to a background prop or import as a background image. Next create your "foreground" like adding figures and other stuff. Using the saved camera and lights just render. Sometimes, depending on your image or the background prop, there might be a obviously visible horizon line twixt the 'foreground'. Thats easily fixed by hiding it with a prop like a wall or hedge. Or just postwork it out. You can also play with this further by rendering it as 3 'planes' background, midground and foreground. Then import each plane in a transmap. For a nice toon effect, dramatically adjust the blur levels on each plane.

Pinky - you left the lens cap of your mind on again.