This is the map of Krakow which I used for much of my research into locations, streets, and area for the city. This map is dated around 1943, when Life Unworthy takes place and shows up in a small section on the book cover being revealed by the wolf's claw.
Many of the key areas and locations mentioned in the story can be spotted on this map, such as the castle and the river Vistula winding through the south of Krakow. The ghetto was south of the river.
A painting of Princess Wanda by Polish artist Maksymilian Antoni Piotrowski.
One of the legends that comes up in the story is of her sacrifice to stop a German invasion. There are various versions of this story, but the one I used is how Wanda commits suicide by throwing herself into the Vistula river. Her beauty was so great that suitors kept coming into the region to demand her hand, and she knew they would never stop as long as she was alive.
As part of the effort to obliterate Polish culture, Hans Frank had much of the art from Poland destroyed, but this painting survived.