I started an idiom project with my kids last fall. Unfortunately I dropped the ball and ran out of time. There were several kids who really enjoyed it. I started with a book about idioms, they were listed and defined, and asked the students to pick one. Next, they worked in thumbnails to depict this idiom, such as Looking Daggers or Full of Beans. The illustration they were to complete should have been a gouche and ink drawing that they would scan and manipulate, but the scanners were disconnected and not working so I lost momentum.
I can't tell you how suprised I was to see the kids digging on the idioms. It was a very nice process to see them working with ideas, even if they were tried and true cliches. A professor of mine always said we have to work through the cliches first before we can get to good stuff. Ignoring them doesn't make them go away, and cliches are what they are because everyone knows them and they work, so its not all bad.