Freely available or not copyright restricted sources
Following is a list of websites where copyright free and Creative Commons content may be sourced. This list is not exhaustive.
Affect the verb images has photos and illustrations celebrating disabled Black, Indigenous, people of colour (BIPOC)
Biodiversity Heritage Library (via Flickr)
CC Image Search
compfight (a Flickr search tool)
flickr Photograph repository. Search on a topic, refine to a particular licence, and check the data attached to the image.
Gender Spectrum Collection for Creative Commons images of trans people. Under the guidelines at Gender Spectrum guidelines you can use these images for topics like beauty, work, education, relationships or wellness.
iconfinder (free and premium icons)
Images from the History of Medicine (U.S. National Library of Medicine, wide range of topics)
NASA Image Galleries
Noun Project (icons and photos with CC licence, some high-res downloads cost)
Openclipart (wide selection of clipart)
Open I (Open Access Biomedical Image Search Engine, incl PubMed Central, and Medpix et al with range of CC licences)
Pexels (free quality photographs)
Picryl (Public Domain media search engine with mainly historic images)
Pixabay (popular and wide ranging CC0 content)
Stocksnap.io (free stock general photos with attribution provided)
Unsplash (wide range of free photos)
Wellcome images (images of medicine, science, society, culture)
Wikimedia Commons: Images the free media repository. Find images by topic or subject.
Be sure to check the terms and conditions of the site, and in some cases the individual images, for usage rights. Be wary of material found under a CC licence that you suspect may be copyright infringing.