https://pxhere.com – lots of nice textures and photos
https://www.pexels.com/ photos
https://pixabay.com/

https://the-dots.com – just dots

3d models:
https://grabcad.com/
https://free3d.com/
https://sketchfab.com/
https://www.thingiverse.com/

https://www.cggallery.com/tutorials/displacement/ – strange displacement