In all forms of artwork, there is the concept of layers.
The Mona Lisa is layered in front of the countryside, which is layered in front of a lake.
In this shot from Borderlands 2, we see the enemy behind the protagonist’s gun, which is layered behind the hud.
This scene from Shrek features Donkey, who is situated in front of Shrek, who is situated in front of a sunflower field.
It is layering which makes an image more complex and more interesting. Depth is definition and definition is narrative. Take this narrative for example.
Here is how I have construed that scene.
The individual featured in the narrative is clearly an outcast, so I have done away with any sort of colour, opting only to work with white, black and the spectrum of grey. The layering of this image also implies separation, as the individual is layered behind glass doors and the bed frame. Additionally, I went for a rather unrealistic portrayal of individual because the narrative is not exactly centred in reality.
Style of art should always follow style of narrative.