I am not sure when the first die maker had the idea of stamping a piece of sheet metal to use as a ceiling tile. Many metal ceilings have survived to this day and are usually coated with several coats of paint.  We have done several ceilings in copper, the copper is stained then sealed with a clear coat to sustain its beauty. We have done them in kitchens, lounge areas and a domed ceiling above a wet bar. Strategically placed lighting illuminates the variety of colors in the stained copper.