When adding images to your documents or web pages/WordPress pages, to meet best practices around accessibility you need to add appropriate descriptive text to your images so that learners who can not see the images have an alternate way to access the images. But adding text to images can be tricky when you are dealing with more complex images like graphs, maps, diagrams, charts, etc.
This Complex image Accessibility site (which opens in a new tab or window) from Portland Community College has some excellent guidelines for how to make complex images accessible to all.