I thought of one!
I saw a tutorial in a magazine on how to make your own washi tape. I used packing tape, a design from a magazine and a little water.
1. Find a design from a magazine you like. The thinner the paper, the better.
2. Put your packing tape on the magazine paper and press down to stick it to the page. You may want to use a bone folder to smooth it down & burnish it really well. Cut the paper out of the magazine. It doesn't have to be perfect.
3. Get a shallow tray & fill it with water. Put your tape in the water & let it soak for a few min. After 3 minutes or so see if the paper will rub off. If not, let it soak a little longer. When it's done soaking, rub all the paper off & let it dry.
Done! The only thing is that it's not sticky so you will need spray adhesive or something else to adhere it.