A colleague and friend of mine (a talented software guy and big fan of all things Scottish) created a screen saver that programmatically iterates through an infinite array of feasible tartans.
Note that by feasible, I mean that the thread patterns and colour ratios follow the rules that tartan designs follow. That does not necessarilly mean that the tartan displayed at any given time actually exists, but it is a lot of fun none-the-less.
I’ve already given him a bunch of features ideas that might make it in there over time, and if you want to pass any ideas on please add them to the comments and I’ll make sure he gets them
Check it out at http://www.strangedynamics.com/plaiddy/