Listed below are a number of resource sites where you will find tens, even hundreds, of thousands of beautiful images available for use, most including commercial rights, for free. Many of these images are still protected by copyright but are released under specific license allowing use without purchase or royalty payments. See below the list for more about licenses.
1. Unsplash
License: Creative Commons Zero. They add 10 new photos every 10 days.
2. Realistic Shots
License: Creative Commons Zero. They add 7 new photos every week.
3. Pixabay
License: Creative Commons Zero. Over 320,000 free photos, vectors and art illustrations.
4. Life of Pix
License: Creative Commons Zero. Why it's great: Photos are broken down by category in their gallery.
5. Gratisography
License: Creative Commons Zero. High-resolution and high-contrast photos, with new photos added weekly.
6. Free Nature Stock
License: Creative Commons Zero. Stock photos of nature only, updated daily.
7. Magdeleine
License: Creative Commons Zero. Sort photos based on colors and tags, updated daily.
8. Snapwire Snaps
License: Creative Commons Zero. 7 hand-picked snaps every 7 days, completely free.
9. StockSnap
License: Creative Commons Zero. Awesome search function with hundreds of hi-res images added weekly.
10. Kaboompics
License: You can use the images nearly any way you want, commercial or not. Several different categories of photos, updated daily.
11. Public Domain Archive
License: Images are public domain. Everything you need for creative projects, updated weekly.
12. Travel Coffee Book
License: Creative Commons Zero. 10 new photos every 10 days of beautiful travel moments.
13. ISO Republic
License: Images can be used for almost any commercial project. High-quality free photos for any creative project.
14. Foodie's Feed
License: Free to use, modify, and edit for commercial purposes. Free high-resolution images of food.
15. FuriousCamera
License: Creative Commons Zero. Free lifestyle photos to use on commercial projects, updated daily.
16. MMT
License: Creative Commons Zero. See License on homepage. Updated weekly with a lot of great nature and city photos.
17. Jay Mantri
License: Creative Commons Zero. See License on homepage. Beautiful landscape photography. 7 new images added every Thursday.
18. Camarama
License: Creative Commons Zero. See License. Beautiful stock photography updated weekly.
19. Cupcake
License: Creative Commons Zero. Stunning landscape and nature photography from Jonas Nilsson Lee.
20. Startup Stock Photos
License: Free to modify, edit, See License on homepage. Stock photos for startups and tech related businesses.
Be sure to check the license requirements at each site (and sometimes for each image). While the images available on these sites are royalty free (no payment required) to use, some have restrictions on where or how they may be deployed, editing restrictions, etc. Most of these images are still the copyright property of others. The license simply grants you permission to use them within the terms specified.
Click to see the Creative Commons Zero License.