Interestingly, I find that coloring book pages work quite well for this technique because of their generally simple designs and bold lines. I've also downloaded images from the internet, or used the customer's party decorations as a template. You just have to be able to trace the design onto a sheet of wax paper (or regular paper). I usually use pencil and then go over it with clear piping gel. Then, I flip the paper over onto the cake and gently rub it to be certain that the piping gel sticks to the buttercream icing (or fondant, as the case may be). Next, I carefully remove the paper. Now, I'm able to re-trace the outline of the image with colored piping gel or icing and begin filling in the design with stars, just like I would have done if had used the shaped character pan.