Art

Offers nearly 400,000 images of works of art from the Museum's collection, including a search function.

https://github.com/heyalexej/awesome-images

https://search.creativecommons.org/

http://blog.stcloudstate.edu/ims/2014/06/01/social-media-and-presentations-free-image-sources/

http://www.nypl.org/research/collections/digital-collections/public-domain

https://www.pexels.com/

http://pixabay.com/en/

https://stocksnap.io/

https://www.istockphoto.com/thinkstock