eBook publishers are working on projects to be released online. Their publishing costs are reduced because no paper is involved. This gives greater flexibility to using color images and the control and ability to edit microstock images and re-use them makes a personally vended low cost legal images feasible. Graphic designers can improve the image by adding design layers with mist, abstract, sharpening, texture, designs or effects. Check out some ebooks art of physical book jackets to get the idea. Original arts sells a product. Index your photos by keywords so potential clients can locate good art for their eBook jackets or vanity press publications.
If you happen to have an outstanding photograph, market the photo (with a watermark inside it ) to specific contact emails of websites of the topic or subject. Keep track of what sites you send the marketing emails to and put them in a folder for future reference. These can get ezine editors planning an editorial