You may want to check Dingleberry Dump.
https://opensimworld.com/hop/93326
Hicks Adder has dumped a number of PBR materials there, but only PBR materials, nothing for Blinn-Phong fallback.
I have a few there myself, mine come with textures for Blinn-Phong fallback materials so that Firestorm 6 and Singularity users don't see everything in grey (I'm almost the only one who supplies these) as well as a manual notecard that explains how to convert downloaded PBR materials into both OpenSim PBR materials and Blinn-Phong maps.
So far, all I have is some leather, some fabric and a rubber floor, all made by Juno from ambientCG materials for various experiments. Many more are in my pipeline, brick walls, tiles, wooden floors, concrete etc., but I don't know when (and where) I'll publish them.