There is a great tutorial for turning photos into cartoons that can be printed with a Gocco here. I think that those of you with thermofaxes could use the same steps to produce artwork for your screens too. The software (GIMP) that the Melbourne folks used is free and with their step by step instructions, the results are fun. No doubt, Photoshop can be used the same way....but don't look at me... I can't tell you how.
Here is the result I got from my first attempt, using an old photo of my girls Trick or Treating in zebra costumes: