The Buddhist motif
The reader may be familiar with the Western equivalent of "Bardo" which is Limbo. Instead of picking Limbo, though, Saunders picks the Buddhist holding place of Bardo, referencing the Tibetan book of the dead. This decision has echoes throughout the book, because Willie depends on certain events in real life to pass through his state after death. This places the entire story of Abraham Lincoln's life within the frame of Buddhist theology/folklore.
The allegorical guides
In the Bardo, Willie meets some people who died around the same time as him. These two men are symbolic guides for him, because they knew more about life. They also symbolize his tragic, young death, because they are older men, so their death is contrasted with Willie's, who died at only eleven years of age. They understand the stakes of his journey in the afterlife and help him to see the severity of his need to pass through the Bardo.
The stuck girl
There is a girl that Hans and Roger remember who never got through the journey of death to her next life, so she was stuck for all eternity in the Bardo. She symbolizes the stakes of Willie's journey, but she also symbolizes the converse of it, because Willie will succeed, but the girl does not. This is also suggested by their different genders, as if to suggest comparison and contrast.
The ghostly motif
There are cemeteries, ghosts, entities, and spirits that all have specific desires for the waking world of "real life." This forms an underworldly, ghostly motif that helps to provide an ominous overtone to the story. Willie's journey through death is shown to be horrific and tragic, as well as sublime and mind-bending. The question of the supernatural is on full display throughout the novel.
The Lincoln reference
To use Abraham Lincoln as a real symbol does a lot for the novel symbolically, because he symbolizes so much in American history. His legacy is that he set the slaves free to end the Civil War, but then was executed. When he dies, that is a symbol for Willie's salvation. This flips the story of Abraham Lincoln's tragic death on its head, because it suggests that he had to depart the earth to save his son, which adds to the Buddhist motif, and it helps to frame a philosophical argument about life, death, and the strange coordination of fate.
