they are put out for people to use to make their own new years cards (in japan, sending new years cards is a very big deal, christmas cards are not). new years cards are postcards, usually featuring a design that incorporates some version of the coming year's zodiac animal (2011 is the year of the rabbit, or usagi in japanese), and some phrase celebrating the new year.
the stamps in the box in this photo include lots of bunnies and also 'happy new year' phrases. what I love is how the post office provides this public (and free) crafting activity! there are black and red stamp pads, rubber mats (dark orange in the photo), tissues and scrap paper for trying out your designs.