Stock images or stock photos are images in which users who wish to use them must first pay a license fee. Many stock image users either pay one-time license fees for individual images or they pay subscriptions to access collections of stock images for their websites or businesses.
If you pay a license fee or subscription to use stock images, you do not actually own the rights to the image; you only pay for a license to use the image in certain contexts, which is stipulated by the terms of the license agreement. For example, a stock image's license may stipulate that you can only use the image for noncommercial purposes.
Furthermore, you are legally obligated to pay the license fee or subscription cost before you can legally use the image in any given context. You cannot apply any copyright exemptions, such as fair use, to your use of the image without first paying the fee. The license trumps the exemption. In other words, no matter how you try to argue it, stock images and stock photography require that you pay the cost that they ask in order to legally use the image in your own work (e.g., on your website, on a poster, etc.).
In addition, some stock image licenses have expiration dates, meaning that you are only paying for a license to use the image for a certain period of time or until a specific date. Sometimes, these expiration dates are only related to the user's subscription, so you may not be able to legally use the images after you cancel your subscription. For example, if you have stock images on your website after the expiration date, then the rights holder could come after you for copyright infringement the day after the expiration date.
It is best to always read the terms and conditions of the license agreement before you decide to purchase any stock images.
For free alternatives to stock images, you can search for images and other works that are openly available. Such openly available works can be works in the public domain and works that have Creative Commons Licenses (CCL) attached to them. "Openly available" means that there is little to no copyright protections attached to the works. The public domain includes works that do not have any copyright protection (e.g., the copyright term expired), and CCL works are works with open licenses attached that allows for generous reuse by the public.
