I had been playing around with Inkscape again, and you can see the result here. I created a geometrical design which I uploaded to Zazzle in order to put it on products in my shop. I had done a rough pencil sketch first and then scanned the sketch in. I imported the sketch into Inkscape, but after some time trying to trace the sketch I decided to only use it as a kind of rough orientation.
I plan to add the design to more and more products.