This is an Eric Karl inspired collage.  Students use a special paint to cover pages with various colors without a concept in mind yet.  The students can use pencils and other art tools to create textures in the paint as well.  Next the students come up with whatever scene they want and cut out shapes from their pages of color.  My example is of a bird who is letting her baby fly for the first time. The student can add as much detail as he/she wants. 
As an extension activity, I can see myself using this concept first for Language Arts or a Reading activity because the student would create a picture based on what he/she read or is working on.  Another way to incorporate this activity is in Science maybe when talking about the planets.  The students can use this process and then make a scene of the planets, starts, or moons.