Last night in flipdot - hackerspace kassel: The T-Shirt Printer dit its first artwork: Printing with an marker pen on a real shirt. The printer firmware has a lot of headroom for improvement - actually its pretty dumb. But the java application converting an jpg to an stream of ascii characters according to the brightness of each pixel works well (thanks elektrowolle!)
Tnx for your feedback! Vectors would be nice if we got solved that problem with the ink, in our case a rather viscous liquid. An other option is vector cutting that special adhesive film you can iron onto the shirt afterwards.