Here is a collection sites that offer free stock images you can use for your projects. Please check the current licensing status for each site as it might have changed as of writing this.
Unsplash - Beautiful, free photos. Gifted by the world’s most generous community of photographers
http://thestocks.im/ - the best royalty free stock photos in one place
https://www.splitshire.com/about/ - Helping you to be awesome out there with great content.
https://picjumbo.com/ - picjumbo is free stock photo site created by designer & photographer Viktor Hanacek in 2013.
http://gratisography.com/ - Free high-resolution pictures you can use on your personal and commercial projects. New awesome pictures added weekly! All pictures were photographed by Ryan McGuire and free of copyright restrictions.
Startup Stock Photos
http://startupstockphotos.com/ - Free photos for startups, bloggers, publishers, websites, designers, developers, creators, & everyone else.
https://negativespace.co/ - Beautiful, Free High-Resolution Photos with No Restrictions For personal or commercial projects, all of our CC0 licensed images are completely free to use!
Life of Pix
http://www.lifeofpix.com/ - Free, high resolution photography.
http://www.endlessicons.com/- Endless Icon is a project bulid by Min Kim who runs Email-Gallery, App Monstr, and Endless Photos. I created it to share some of the icons and creative stuff with the design community. Cheers!