I love paint-by-number. I used to do it when I was a little kid. Now software turns your photos and graphic art into paint by numbers. They might be a little pricey, but add 50% to your cost and sell them. If it cost you $50 to create your PBN, sell your PBN to a customer for $100. People pay a lot of money for art, and if they can paint a picture they like that you created, they will probably pay the money. Find your audience.