Corbis, a leading provider of stock photos, is doing away with its fee-based model in some instances, opting instead to let bloggers use the pictures for free if they agree to showcase the ads embedded in the images.

The photos will support two ad units: an overlay or a pop-up that engages when a user runs their mouse over the correct part of the image.

The program, known as PicApp, allows bloggers to share in ad revenue.