Do you have a couple of minutes a the end of class? Do you have an interactive board? I have just the site for you...
http://www.jacksonpollock.org/. I used this as a reward for students to get in line. If we cleaned up faster then expected I ask each student to come up by tables and make a 'Pollock mark' on my Smartboard. I explain how Pollock uses his whole body and canvas to make his art. They make a mark on the board and get in line. The kids LOVE it.