In Japan, there is a postcard called regional form card, it's a postcard which is unique to each prefecture. They always features the famous product, travel spot, animal, food, sport team in respective prefecture. Like the postcards shown in photo below.
These are the two famous food in Hiroshima featured on the postcard above:
There are many more postcards in different shapes, different colour and different characteristic.
All of these postcards are all bought in different prefecture's post office, for instance, you won't find Okayama's postcard in Hiroshima's post office. Unfortunately, it cannot be sent outside of Japan.
You can find out all the designs of all the regional form card on this website:
Besides the prefectural postcards, there are some cute die-cut postcard for each season too.