I once did a project with my 3rd graders where we looked at a bunch of poems and cartoons from The New Yorker and then they tried to do one of each. It seemed like almost all of the adult poems had death as a major theme, so I specifically told them something like "that's a topic for old people, try to write about Life instead." I sent them outside to look at something in "Nature" (well, a suburban school playground) and come up with a metaphor for their poem. The only rules for the cartoon were, one picture, one line, and both should be necessary. Humor preferred but optional, same for social commentary. They came out surprisingly well as a whole, and I bound them as "The Third Grader" for the class library.