What are some examples of symbolism in The Book Thief by Markus Zusak?

A symbol is an object or person that stands for something other than itself.  I will give you an example of an object and a person.  An example of symbolism in the story is the books that Liesel steals, and the act of reading itself, which both represent freedom and escape.  Liesel finds herself in a very difficult situation. She has lost both of her parents, and her brother.  She lives in a country and a time ravaged by war.  Liesel is unable to read when she steals her first book, but she uses it to learn.  Books become her salvation.

When she came to write her story, she would wonder exactly when the books and the words started to mean not just something, but everything. (Ch. 3)

To Liesel, reading is more than a pleasurable pastime.  Books are very valuable to her.  This is why she steals them, because she doesn’t have access to them. The very act of stealing them is a symbolic act of self-expression.  It demonstrates the crushing nature of Nazi Germany and how small acts of expression can make a difference.
Another symbol in the story is Jesse Owens, the Olympian.  Rudy is obsessed with Jesse Owens because he is impressed with his physical feats.  As a boy, Rudy appreciates that Owens can run.  Race does not matter.

Even the most racist Germans were amazed with the efforts of Owens, and word of his feat slipped through the cracks. No one was more impressed than Rudy Steiner. (Ch. 5)

His father tries to explain to him that Owens is unpopular in Germany because of his race.  Jesse Owens thus becomes a powerful symbol of the disconnect between what Germany values (race) and what it should value (achievement).  These are just two examples of symbols in a book full of symbols.