Below is a list of websites offering images, photos and videos that are released free of copyrights under Creative Commons CC0. You may download, modify, distribute, and use them royalty free for anything you like, even in commercial applications. Attribution is not required. You are allowed to use these photos in your website templates for sale.
Top 24 free stock photo websites

Kaboom Pics
kaboompics.com Free images of the highest quality, constantly growing image database.

UnSplash
unsplash.com Rich collection of nature photos promising 10 new free images every 10 days

Realistic Shots
realisticshots.com Free stock photos for personal and commercial use. 7 new photos every week.

Pixabay
pixabay.com over 45,000 high quality photos, illustrations, and vector graphics - CC0

Life Of Pix
lifeofpix.com 800 photographs all donated to public domain. New ones added weekly.

Gratisography
gratisography.com free high-resolution pictures, new one added weekly.

Free Nature Stock
freenaturestock.com Royalty-free Nature Stock Photos.

Magdeleine
magdeleine.co hand picked photos, most images are CC0 but some require attribution

SnapWire Snaps
snapwiresnaps.tumblr.com Photos from 200,000 of the world's most talented photographers

StockSnap
stocksnap.io Hundreds of high resolution images added weekly. Free from copyright restrictions.

Public Domain Archive
publicdomainarchive.com a repository of public domain images found across the web

Travel Coffee Book
travelcoffeebook.com - Sharing beautiful travel moments.

ISO Republic
isorepublic.com - Free stock photos for creatives.

Foodies Feed
foodiesfeed.com - Free food pictures. You need to share to get the download link.

Furious Camera
furiouscamera.com - free search engine that searches 30 other stock sites.

MMT Stock
mmtstock.com Free photos for commercial use. New photos each week. CC0 license.

Jay Mantri
jaymantri.com - free pics. do anything (CCO). make magic.

Cupcake
cupcake.nilssonlee.se Free (do what ever you want) photos.

Startup Stock Photos
startupstockphotos.com Free photos for startups, bloggers, publishers, website designers & developers.

Pexels
pexels.com over 30,000 free stock photos.

Negative Space
negativespace.co Beautiful, Free High-Resolution Photos with No Restrictions

PicJumbo
picjumbo.com photos by photographer Viktor Hanacek.

Monis Photo
monisphoto.com unique free stock photos

AvoPix
avopix.com Stock photos and videos, updated daily.