The art design was based on German Expressionism and medieval German art conventions. Barta said: "This element has actually solved certain spatial problems in that part of the mediaeval canon is that the important figures are big, and secondary figures are small. So it has solved the whole problem of space, and justifies an illogicality – a lack of logic – about the world of the film." Barta designed the puppets and sets himself. He started with drawings and then made models to provide three dimensions. The puppets were intentionally designed as to appear mechanical, which would contrast with the use of living rats, to create the impression that the rats were more alive than the humans. The exceptions were the characters Agnes and the fisherman, who were given a softer design to represent a world of purity. The puppets varied in size between one and 60 centimeters. One scene in the film features two-dimensional animation in a style radically different from the rest. This segment was inspired by medieval painting on wood, and in particular the art of Jan van Eyck.
