Open Peeps is a hand-drawn illustration library of people created by Pablo Stanley, which is free for commercial and private use under CCO Licence. The library even allows you to mix and match clothing and hairstyles of the drawn people.
Old Book Illustrations is a searchable database of scanned old book illustrations. Included on the site are a number of illustrations from Irish artist Harry Clarke.
Designs.ai provide a set of AI powered design tools that help the user get graphic design work done without the need to have too much graphic design experience. The company have two paid AI products on offer, logomaker and videomaker. They also offer a set of free assistive tools, including a colormatcher, a palette selection tool using AI generated colours.
Public Domain Review have posted a fanstastic piece on book covers from 1820 to 1914. New mechanical binding techniques and cloth printing form 1820 allowed book covers to become a new artistic space. Feast you eyes on some glorious examples here.
The Instadeq Blog has a great list of things that end users care about but programmers don't, such as "Use the fonts I use in Office" and "emoji support".