Mosaic Art Pictures.
A set of 5 postcards, each of which has a simple pattern. At first, they just seem to be a random collection of coloured squares. But as you hold each postcard further away, the squares start to blur slightly, and you should be able to see a famous picture.
The pictures are
Girl with a Pearl Earring, Johannes Vermeer
Mona Lisa, Leonardo da Vinci
The Scream, by Edvard Munch
The Great Wave, Katsushika Hokusai
Otani Oniji in the role of the Servant Edobei, Toshusai Sharaku
With the exception of maybe the last one, these are all quite well known pictures. We have found that you need to be at least slightly familiar with the original painting, in order to be able to 'see' the mosaic art card version.