What are some alternatives?
When comparing Stubborn Illustrations and Open Peeps, you can also consider the following products
Evie by unDraw - MIT licensed illustrations for your next project
Humaaans - Mix-&-match illustrations of humans with a design library.
DrawKit - MIT licensed SVG illustrations, in 2 styles
Blush - Illustrations for everyone
Handsome Illustrations - Create unique illustrations for websites & applications.
Avataaars - Mix and match avatars with a Sketch library