Using stock images or photos is indispensable for creating digital content. Pexels is one of the free stock image websites that i am using for my website & blog content and presentations. There are amazing shots that you can easily select by categories and download them. The only thing you can do is donating them via Paypal. If you are searching for websites, just refer to the free stock photo wunderlist of mine.
Here are the shots that i use & love.
Free Stock Image website pexels.com