These are images searches that offer searches for free images:
Unsplash: Free High Quality Images
Unsplash offers free high quality images from photographers. The images are free for anyone to use. Photo credits are requested by not required.
Most of the images on Greycoder where found on Unsplash. The image featured above is by Drew Graham on Unsplash.
Pexels: Free High Quality Image Search
Pexels is very similar to Unsplash but features a smaller catalog of photographs. The images are free for anyone to use. Photo credits are requested by not required.
DuckDuckGo Private Image Search (Large Images Only, No Pinterest Results)
This search uses the private DuckDuckGo image search engine. It is set only find large images, and avoid images from Pinterest.
Bing Extra Large Image Search
This is a Bing image search. It is set to only find extra large images.
Behance: Artist Portfolio Image Search
Behance has a large catalog of photographs and illustrations from artist portfolios.