"In Hanover Germany, children's advent calendars now feature the image of serial killer Fritz Haarmann lurking behind a tree. During his murder spree in the 1920s, the 'Butcher of Hanover' killed at least 24 young men (mostly prostitutes), chopped up their corpses and possibly sold their meat. He was apprehended in 1924 when a number of skeletons washed ashore in the River Leine, which happens to be the very river he's posing next to in the picture, axe in hand. Ananova reports that tourism board head Hans-Christian Nolte, defended the calendars stating 'He is part of our city's history.'"
through the link, you can see the actual picture used in the calendar. it's cute and comical, the way he is portrayed, but still in there. subtle messages to keep children in line, perhaps?