Use Value Change
To Create Depth
In real life there is dust in the air that filters the light from distant objects. Things far away are muted. Things close up are in sharp contrast.
If you reverse the values you get a night scene.
This works because at night things close up are well lit and distant things are in the dark.
You can use these effects to create depth in your quilts and you don't have to do the traditional mountain scene. Just remember that things that contrast strongly with the background move into the foreground; things the are close in value to the background move back.
How far something moves forwards or backwards depends on how much it contrasts in value with the background.