These are all great suggestions . Another way to transfer an image onto a cookie is to use Marilyn's method, Montreal Confections, as shown in the UTube link here:
She uses an embroidery hoop with mesh inside the hoop (pulled taut), Marilyn then pipes the main lines of the design you want to copy directly onto the mesh. She then places the mesh hoop with the piped design on top of the cookie and uses an airbrush to spray color over the cookie. The RI lines will turn out white on the actual cookie after it's been airbrushed. Then you have an easy guide to follow directly on the cookie. I hope this also helps!
The reminder of this video method was given to me courtesy of Donaharrisburg! Thank you Dona .