List of free illustration stuff for developer👇🏽
If you're looking for all programming tools around illustration (not just free). Check this page List of illustration Programming Tools

Dribbble
Dribbble is an online community and service for the exhibition of artistic content. It works as a self-promotion and networking platform for graphic design, web design, illustration, photography, and other creative areas
Tag: design, web-design, illustration

Open Peeps, Hand-Drawn Illustration Library
Open Peeps is a hand-drawn illustration library to create scenes of people. You can use them in product illustration, marketing, comics, product states, user flows, personas, storyboarding, quinceañera invitations, or whatever you want! ⠀
Tag: asset, illustration

designstripe
A constantly growing library from our Studio team, all completely customizable online
Tag: illustration, design, asset
1 illustration style Access to the Cheerful style only Full scene customization PNG, and JPG downloads

Open Doodles - Free sketchy illustrations
A library of sketchy illustrations of people free for personal and commercial use.
Tag: asset, illustration