I am going to approach this in terms of scene planning, take note that this is in no intended to be a "How To" on background ground layouts or painting but simply a "something to think about when planning your shots/scenes." Some links on this topic are here, here and here (There are so many but I don't want to get carried away).
Planning a scene is a lot like planning a a painting; you must decide what is to most important and then work your way to least important. If something has no importance it must be taken out of the shot-everything to be shown must be of some importance, even if it only adds to the composition. So a first step in planning your shots would be to ask if all of the background subject matter is necessary as well as how the elements in the BG work to achieve a solid composition.
image above, Rembrandt chose to position the main figure (Christ) higher to show his significance as the other figures (the sick) swarm around him. The dark tones of the building in shadow behind the main figure out create an contrast from the foreground elements. The shadow of the archway frames the action as light spills from right to left. The darks and lights make the visual hierarchy clear.
Below, in this drawing by Charles D Mitchell, storytelling is very clear but layout is much too flat to allow for the characters to move freely in the space due to the cluttered chairs etc.
Giovanni Bedini from 1924. Here, a young woman plays a violin with such a charming expression and character that it is hard not imagine walking into this scene where she plays just for the viewer. The darkest and lightest elements lay atop each other on the right third of the painting and the painting seemed designed to allow the woman the ability to get up from her work and move around the space. It's this, seeming openness of space that is what sets layouts and BGs apart. Like real spaces, a character is able to "move" around in these imaginary environments.
Scene planning begins with the script/storyboarding phase. Concept art is generated while story is in development to craft the look of the themes, places and anything that will be involved in the story. Concept development may give a snap shot of look of a moment but may not focus on setting a stage for animation as this painting from Marc Lumer for The Emperor's New Groove.
drawing below. As seen, there is little room for a character to actually move around in the spaces provided here.
camera angles would be best to describe the story and action is mapped out. In this storyboard image from Batman Animated Series we see the camera has been planned to show the Penguin aiming up at an onrushing Batman. The camera tilts up and dollies into Batman, then tracks his progress right as machine gun fire explodes around him.
Balto followed by an example from Gulliver's Travels. In both, the spaces designated for the characters to traverse are pretty clear.
Animation Treasures (an awesome blog). Clearly the dogs would mount the hill.
layout, Cruella speaks to Horace and Jasper from her phone on the bed in long shot. This shot followed by a close up for better staging of character action. This is a great drawing though, so I had to post it.
Ralph Bakshi's Lord of the Rings...
Chuck Jones' Riki Tiki Tavi. This is down shot which pans to follow the action of the characters as they move through the garden.