Oh! I remembered my favorite!
I made a backdrop for my photo studio trying to recreate a wall I had seen in some movie.
I bought a huge piece of vinyl flooring, painted the back of it with red primer and glued on a million tiny squares of copper leaf, burnished the whole shebang with the back of a spoon, aged it with some thin black paint and varnished several coats of umber on top.
The only evidence I still have of it is sadly a black and white photo where you can't see much of it...