Pixabay
With the Pixabay module you can insert images directly from Pixabay into your website. The only requirement is an API key from Pixabay. To get this go to https://pixabay.com/service/about/api/ and then enter the API key in Settings -> Modules -> Pixabay.
After this is inserted you will see a Pixabay tab when inserting images in the WYSIWYG editor and Web Builder.