Today I got the PCB coaster from Adafruit. They look so much better in real than on the photos in the shop. The coasters are made from 2.4mm FR4 PCB material. There is a transparent solder mask on the top to protect the copper and gold elements. The frame around the image is black silkscreen.
I really like the combination of the cold and coper colours.
The coasters were designed by Saar Drimer at Boldport. You can buy them in the Adafruit shop.