Creative Commons Photos
It’s hard to understand complex licenses that is why all photos on Pexels are licensed under the Creative Commons Zero (CC0) license. This means the pictures are completely free to be used for any legal purpose.
Also WP Tavern has a blog post 13 Sources For Free Public Domain and CC0-Licensed Images
A while ago, I found another great resource on where to find photos, graphics, icons, and more — particularly, ones free of copyright restrictions.
From Toronto-based web designer Steve Benjamins – last updated Feb 12, 2014.