Don Masse, an elementary school teacher at Zamorano Fine Arts Academy in San Diego, created an assignment using art from Foster's Home for Imaginary Friends to teach foreground, middle ground, background. Zamorano is an art focused elementary school that serves a diverse population of students.
The Foster's BGs below were used as examples
All rights to Foster's designs belong to Cartoon Network
The children created the images below using cut paper for a background, then applying a middle ground layer, and a foreground on top.
The teacher's blog has more information: Zamorano Fine Arts Academy