Isometrica - 3D illustration constructor with 380+ isometric objects
Characterz - Biggest diverse mix and match 3D illustration library
Khagwal 3D Illustration Library - Free 3D illustration library for web & mobile app designers
3D Flame Illustrations by Icons8 - Eye-catching 3D illustrations for kick-ass designs
Humaaans - Mix-&-match illustrations of humans with a design library.
Free 3D Slam Illustrations - Virtual reality gadgets are embodied in volumetric graphics