All images need an alternative tag for people who cannot see, or who have technical problems with images, for example low bandwidth. See the course "Writing for the web: Readability and the Local Offer".
Colour contrast ratio
People with poor vision need a clear contrast between buttons and the background, for example.
Web Content Accessibility Guidelines (WCAG) requires a minimum contrast of 4.5 to 1.
Use the WebAIM Contrast Checker
Royalty free and Rights managed
The "free" in royalty-free does not mean there is no cost for the license, but instead refers to being able to freely use the image without paying additional royalties.
Rights Managed, or RM, in photography and the stock photo industry, refers to a copyright license which, if purchased by a user, allows the one-time use of the photo as specified by the license. If the user wants to use the photo for other uses an additional license needs to be purchased.
Easy on the i is a free image bank for making easy read materials
Photo Symbols is a unique photo library. It was created as a tool for people who make easy-read information.
The pictures reflect all kinds of ideas and everyday situations and feature actors with learning difficulties.