Stamps cover all significant events happening in the world. Much attention was paid to polyhedra by artists-philatelists. The stamp dedicated to Leonhard Euler with the image of icosahedron was issued in 1983 in East Germany (200 years anniversary of the scientist).
Another stamp was issued in Switzerland in 2007 and was devoted to the 300 years birth anniversary of Leonhard Euler.
This is the stamp issued in Monaco in 2000. It was dedicated to the Year of mathematics. You can see the image of dodecahedron there.
The stamp issued in Hungary in 1980 depicts Johannes Kepler, a mathematician and an astronomer, and his model of the universe based on regular polyhedra (Issue #4 of Magic Edges).
The stamp issued in Italy in 1994 is dedicated to Luca Pacioli (Issue #3 of Magic Edges). You can see a dodecahedron among various items in front of the scientist.
The stamp issued in Mongolia contains the copy of an engraving by Albrecht Durer "Melancholia". One of the elements in the engraving is a polyhedron, a prism truncated at the top and at the bottom.
In addition you can also see two stamps where you will not find polyhedra in their conventional sense.
The stamp is devoted to the mathematical congress in Innsbruck (Austria) which was held in 1981. It is based on Escher's impossible box.