Source Wireframe Kit - Library of 537 blocks for desktop and mobile prototyping
UI8 - Carefully crafted UI design assets
Form Wireframe Kit by InVision - A free wireframe kit from InVision
Handsome Illustrations - Create unique illustrations for websites & applications.
Contra Wireframe Kit - Open source wireframe kit for design and prototyping 🚀
Ouch! Illustrations by Icons8 - Professional, perfectly matching, and customizable illustrations for any designs