So far there are 24 illustrations licensed under the Creative commons - attribution, share-alike - license, which means you may do anything you want with them, including changing them however you wish and selling them for profit, as long as the source is mentioned and the resulting artwork is also made free to use under the same conditions.
We've used them to make some posters, and pictures for the dojo. Like the one below. You can download the collage, and the individual pictures from: http://www.flickr.com/photos/hultstrom/sets/72157632298341948/