Hi everybody !!
I had the pleasure to be a Material/Environment Instructor along 2 years !! I've teached to EICAR Paris, SAE Institure Paris and LISAA Paris Video Game for Bachelors 1/2/3 and Masters 1/2 promotions.
Here are some examples of materials 100% Substance 3D Designer made in class room for my students.
My photo references are coming from Textures.com scans mainly. Then you should probably find similar materials on this website.
The goal was to find great references from reallity, a good way to do it is from a scan to show you multiple renders like a gray render to show you only how's reacting an Height map and a Normal map for example :)