Repeat patterns!! What an intriguing concept. This is probably old hat to you graphic designers out there. I saw a photoshop how-to in a magazine a year or so ago, but didn’t get around to it at the time. As I was contemplating fabric design and thermofax printing screens, the technique bubbled up and a quick online search led to easy directions from Julia Rothman: http://www.designsponge.com/2008/05/welcome-julia-and-how-to-make-a-repeat-pattern.html. Give it a try!
Very easy to do in analog mode; perhaps something your summer tweens might enjoy!