Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Open Peeps - A hand-drawn illustration library.
Icons8 Lunacy - Free graphic design software with built-in resources. Fully compatible with Sketch and works offline
Control Illustrations - 108 free flat illustrations with customizable characters
Adobe XD - Adobe XD is an all-in-one UX/UI solution for designing websites, mobile apps and more.
DrawKit - MIT licensed SVG illustrations, in 2 styles