Recently a client asked about the best stock images that had a free license and I had a few come to mind. This got me thinking about how best to integrate this info directly into Craft and allow for the authors to get some credit. There is a nice plugin called Splash (https://github.com/ethercreative/splash) that was created by the same people that put out a good free SEO plugin. This plugin allows you to search and download images directly into your assets directory in your Craft CMS instance. It allows you to map the Author, Author URL and Main Image Color. I have been testing this out on my website and have created fields in the assets to map the images data.
Unsplash does not require you to attribute the source of the image, but I find it to be a nice idea to include it somehow if you are not going to put it in the front end of the site. I am testing this on my local development and plan to add attribute data on the backend of the photo to give the author credit. There are many other free stock image sites out there such as Pexels and Pixabay, but I have only found a plugin for Unsplash that is integrated directly with Craft CMS. If you find another cool integration with a CMS, drop me a line.