As you know, this year Poland together with Ukraine was organizing European Football Championships. On this occasion Polish post office issued stamps and I of course bought them :D
I really like those round ones with a ball and flags of both countries:)
There are also stamps with the stadiums in Gdańsk, Poznań, Warsaw and Wrocław.
I actually wish there were more stamps in shapes other than square:P
Do you have some non square stamps in your country?