When I first started going to Cons, there would always be a few people selling postcards. Cards adorned with awesome comic art, movie posters, famous figures and the like. Then in the late 2000's, postcards started to become scarcer and scarcer. In the last couple years, those "throwaway" art examples became buttons and now buttons are everywhere with everything from movies, actors, musicians, cartoon characters, slogans, memes and whatnot. The latest trend sees makers using actual pages from comic books as the image.
Take it away Etsy: