Free 3D Textures:
Collection of 50 Distressed Textures
Quixel Mega-Scans (50 free)
https://3dtextures.me/
https://renderman.pixar.com/pixar-one-twenty-eight
https://www.3dxo.com/textures
Free HDRI Images:
https://hdrihaven.com/hdris/
https://hdrmaps.com/freebies/
http://www.hdrlabs.com/sibl/archive.html
http://www.aversis.be/hdri/hdri-free.htm
Free 3D Models:
https://www.turbosquid.com/Search/3D-Models/free
https://www.cgtrader.com/free-3d-models
https://sketchfab.com/search?features=downloadable&q=malopolska+&sort_by=-relevance&type=models (Museum artifacts -HIGHLY RECOMMENDED)
https://sketchfab.com/britishmuseum/models (British Museum artifacts — RECOMMENDED)
https://www.myminifactory.com/pages/explore (VERY GOOD .stl models meant for 3D printing — you will need to add your own “generic” materials)
http://open3dmodel.com/
http://www.3dchf.com/
https://clara.io/library
https://3dwarehouse.sketchup.com
https://archive3d.net/
http://www.oyonale.com/modeles.php?lang=en
https://free3d.com
https://sketchfab.com/features/download (includes scans of British Museum artifacts)
http://threedscans.com/ (scans of ancient artifacts)
https://www.designconnected.com/Freebies (designer furniture)
https://nasa3d.arc.nasa.gov/models (space stuff)
http://www.dmi-3d.net/ (cars)
http://scifi3d.com/ (scf-fi themed models)
https://www.artec3d.com/3d-models (scanned items)
http://redwood-data.org/3dscan/models.html (scanned items)
https://dimensiva.com/ (requires registration)
https://grabcad.com/ (industrial design, requires registration)