The WordPress community maintains a free photo directory which collects user submitted photos under a Creative Commons license. Each photo is moderated by a member of the Photo Directory Team and is available for free.

The WordPress Photo Directory provides free, high-quality, CC0-licensed, community-submitted photographs suitable for use within WordPress sites and elsewhere.

https://wordpress.org/photos/faq/

The team recently marked the milestone of 5,000 photos which can be viewed at wordpress.org/photos. New contributors are welcome to submit their photos for inclusion in the photo directory.