use an everyday urban object (you might remember from your childtime) and fill it up with good creative local artist work. people pay a small amount to pull a cool, stamped postcard they only have to write.
you get to communicate much easyer with old friends or new, from berlin or all over the world and support the local artist scene.
its also possible to have cards with poems, small stories and other culturel and artfull stuff
artist get fame and some money
sparkasse distributes the creatives and builds up a network which is endless