Froala Design Blocks is using the awesome Open Source illustrations created by unDraw. They have vectorial images that can be customized on-the-fly.
As they say, "simply beautiful open source icons", that's what we are using the Design Blocks. Feather icons created some very nice icons and we are happy to have them in our project.
A photo is worth a thousand words, and Pexels surely knows that. Froala Design Blocks uses photos made by the talented photographers from Pexels.
Communities are great place to get help and Creative Tim is one of our main contributors. With great sense of aesthetics, their designs always stand out.