Looks like treated metal? Maybe steel?
Here is a link that might be useful: Ceiling
Looks like a piece of art in the Andy Warhol Museum... titled "Urine on Copper".
It's acid treated metal. Chemetal makes some real metal high pressure laminates with similar, but I think better-looking finishes.
Here is a link that might be useful: Chemetal
looks like stained concrete. i doubt that's what it is, but i've seen stained concrete floors that look like this in restaurants.
It says in the lower left corner: "rusted metal" Or, do you think someone just titled it that?
It definitely looks just like rusted sheet metal (steel)