The sources listed here have images and photos that can be downloaded for free with no or limited restrictions.
Creative Commons Image Search
CC Search is a tool that allows openly licensed and public domain works searches across more than 300 million images from open APIs and the Common Crawl dataset. Aggregates results across multiple public repositories into a single catalog, facilitates reuse through features like machine-generated tags and one-click attribution.
Flickr
Images provided are listed under "no known copyright restrictions" and can be shared and used with appropriate attributions.
Pexels
Provides high quality and completely free stock photos. No attribution required.
Pixabay
Provides royalty free photos and videos. Pictures are shared as part of the public domain with people all over the world.
Unsplash
Unsplash grants you an irrevocable, nonexclusive, worldwide copyright license to download, copy, modify, distribute, perform, and use photos from Unsplash for free, including for commercial purposes, without permission from or attributing the photographer or Unsplash.
Wikimedia Commons
Wikimedia Commons is a media file repository making available public domain and freely licensed educational media content (images, sound and video clips) to everyone.