Nena (Abbey Hoes) is almost certainly named after German singer Nena, who was very popular in the 1980s with her song "99 Luftballons", which was translated into English as "99 Red Balloons". The scene where Carlo (Gijs Blom) brings Nena a bundle of red balloons most likely refers to the song.
The photo on the wall when Nena is sitting outside on her own and trying a cigarette for the first time, is a portrait of German-language author Franz Kafka.
The topless pin-up girl on the poster on Carlo's door is English pop singer and 1980s' glamour model Samantha Fox.