I may be off base here, but my first thought when I saw you sold digital copies, was that a business person could commission you to create a set of iconic images for use throughout a powerpoint / graphics, to add interest, and pay you for a set of 8. And you keep the rights to the original, but of course, you develop custom ones for the client.
You would need to help get the digital format to something that could be used electronically, however. (?)