The themes of adult coloring books are usually intricate and centered more around adult images, not your childhood counterparts that included bunnies, super heroes, and farm animals. You would expect to see geometric patterns, psychedelic patterns reminiscent of doodle art type pages, fantasy images including angels, dragons, goddesses and mermaids, and ancient designs of religious and spiritual nature.
Coloring in pages that are specific for coloring. I have found a few websites that have pages to color that are downloadable. You can also try a resource store for teachers. These specific pages for coloring are pictures or drawings of a variety of design that you alone enjoy. You can make your own coloring book with these pages. After coloring the designs you can write your own narrative about how you feel. Write how the design itself and the colors you used relieved your stress. You can even write a short story about the design if you like, this is your project and it is for your eyes only.
Coloring books are a thing of the past. Kids today arent as thrilled by a basic coloring book as children a generation ago. That is because these children have been spoiled by all the fantastic new methods of coloring using the computer or with fancy markers and pens. While you might get away with a coloring book and crayons for a long car trip, dont expect your school age children to sit quietly at the table coloring pictures the old fashioned way - there is a something better around, and they know it.