The song that is playing as Magnus enters Benni's trailer is Falco's "Jeanny". In episode 3 of season 1 (in a scene from 1986), this song is being discussed by Katharina and her friends in the hallway at school. It's remarked that the song is about "a man who kidnaps a girl and takes her to the forest just because she's wearing red lipstick. In the end he kills her." The song was banned by some radio stations for its content, but nonetheless it was a huge hit in European countries that year.
The painting featured in Season 2 is The Fall of the Damned by Peter Paul Rubens, painted in 1620. It depicts a scene from the Book of Revelations in which the Archangel Michael throws Lucifer's rebel angels into Hell.
Investigator Clausen is seen wearing Indian Terrain checkered shirt in S2E1 - an Indian local brand famous for their checkered designs.