Valve's HL2 plaster textures...

Example?

http://www.cgtextures.com/ with no doubt an artists touch up

I think they had a spec map and a normal map on the plaster I remember it looking nice, most world textures didn't have both

Quote from D3ads

...are so beautiful. I want to try and replicate them.. does anyone know how they made them? Did they use any stock content from a paid site for them? They look almost too good to be made from just real life photo references.

They used their own photo reference, you can see a lot of overlays/basetextures used on most of HL2 textures, propably also because one guy made them all (world textures that is).