Have a cup of coffee or wine! and relax with the computer. Do an internet search for what ever theme you are looking for. Don't search for cookies. Try searching under things like coloring book pages, embroidery designs, and colors. Use your search tools and narrow it down to "line drawings." I usually end up with more ideas than I have time for. Consider this as artistic entertainment for yourself and enjoy the search!
Great advice Heidi.
Don't do anything that you don't enjoy. That blocks creativity. Every cookier has their own style. Build a nextwork and pass the order along, it'll take pressures off that could be freezing up your creativity.
It's like writer's block. Every great writer experiences it. You're in good company. You'll overcome the issue.