Unsplash is a website specialising in free to use, user submitted, photos of high quality. Here is an excerpt of the Unsplash license terms:
More precisely, Unsplash grants you an irrevocable, nonexclusive 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. This license does not include the right to compile photos from Unsplash to replicate a similar or competing service.
Have you found another, perhaps better, free photo site? Comment below.
(Photo from Unsplash)