Stock photos are mostly for commercial, editorial, entertainment and artistic uses. We saw them on Book covers, Pamphlets, Advertisings, Websites, Tv movies and shows, Newspapers, Magazines, and more ( see this website ) ..
As long as they are labeled for commercial use, you can use stock photos in multiple designs and projects with a for-profit purpose. If the photos are labeled as Editorial, you can only use them for this end (never commercially).