What are some alternatives?
When comparing Illustrio and DrawKit, you can also consider the following products
Evie by unDraw - MIT licensed illustrations for your next project
Flaticon - A database of free vector icons.
Humaaans - Mix-&-match illustrations of humans with a design library.
Font Awesome - Font Awesome makes it easy to add vector icons and social logos to your website. And version 5 is redesigned and built from the ground up!
Handsome Illustrations - Create unique illustrations for websites & applications.
IconPharm - IconPharm is a library of open source icons with recoloring and resizing tools.