I recently designed some Disney Inspired dress designs that I tried to sell as originals. Unfortunately selling original work normally goes outside of people's price range so therefore I wanted to create the designs in a way that could be purchased by anyone of any age. The easier option and cheapest option, is postcards. They're a perfect size that they still hold detail and are great for younger children to send to their friends or perhaps collect.
I currently have four designs; Elsa, Belle, Rapunzel and Aurora but do plan on creating more depending on success.