Adding to the list: Pixels [3] https://www.pexels.com https://www.pexels.com [4] https://www.pexels.com/photo-license/ https://www.pexels.com/photo-license/

Adding to the list: Pixels [3] https://www.pexels.com https://www.pexels.com [4] https://www.pexels.com/photo-license/ https://www.pexels.com/photo-license/ They currently have over 5000 photos (~600 new images are added every month)