We explored printmaking last week. It was the first time for this group of children, so we painted with a single color onto trays that I purchased from the dollar store, and then a print was made by laying a paper onto the paint, rubbing it gently, and then peeling it away.
All of the work was abstract, an exploration of the medium and the process. One child attempted to paint her name, and another painted a picture of a person but painted over it as she explored the feeling of painting on that smooth tray.
I've done printmaking with children before - it used to be a weekly affair. It can be done by covering a surface with paint and then taking paint away with a tool like a Q-tip. You can see some past explorations over here. Time flies!