pexels and flickr are both good for trying to get links.
If you are looking for specific niche-related links from the photos. It might be best to get a lot of construction photos for the construction niche, etc. You cannot really control the sites using it.how does those links perform?
Both make your photos public domain easntly. How well did it work?Unsplash or Pexels. I've used Unsplash for link building with great success.