A few months ago I was looking at a catalogue from a flooring company called FLOR. I spotted that a couple of the pictures of rooms had mathematics on the wall. And not just basic material. One had a commutative diagram with what looked like a piece of a long exact sequence in it. I decided that I had to understand how such a thing could have appeared in a catalogue selling floor tiles.
After a bit of poking around I eventually found the pictures on the company web site, but no clue why they were there. I then posted to sci.math and was eventually led to this article from the Notices of the AMS. It turns out that the artist Bernar Venet specialises in paintings derived from mathematical digrams. He seems to have made a speciality of painting commutative diagrams.