The accordion starts off as a symbol of hope and comfort. When Liesel begins reading to the residents of Himmel Street during the air raids, she feels like she's giving them what Hans gives her when he plays the accordion – distraction, comfort, and hope.
For Hans, the accordion is a symbol of the man who gave it to him, the man who saved his life. That man is Erik Vandenburg, Max's father. For Max, the accordion symbolizes the possibility that he'll survive the Holocaust. It's the link between him and Hans Hubermann, the man willing to risk his life to help him.
When Hans leaves for Essen, he leaves the accordion behind. For Rosa in particular it becomes a symbol of Hans himself. When Liesel sees her wearing it ever night, but never daring a note, she realizes how much Hans means to her foster mother.
When Liesel finds the accordion among the wreckage of Himmel Street after Hans has died, it is a symbol of great loss, but one which carries much of her story within it. It is yet another symbol of the novel's argument that literature, music, and other arts can provide sustenance in times of great suffering.
Adolph Hitler, The Swastika, and The Nazi Flag
Hitler and the Nazi Party used mass communication, like radio, film, and print, to involve the German people in carrying out the Holocaust. To get the job done, Hitler employed a Minister of Propaganda, Joseph Goebbels. Hitler, reproduced in photos, film, and radio broadcasts, becomes a symbol of power and leadership for those who follow him, and a symbol of horror and terror for his targets.
Through the reproduction of his image, his voice, and his symbols – the Swastika and the Nazi flag – Hitler becomes an omnipresent force for everybody in Germany. These are the symbols by which the people are enlisted to support Hitler, and they are backed up by some of the most horrific actions you've heard of. They are, ultimately, symbols of fear, irrational prejudice, and terror.
Today, the swastika, the symbol featured in the Nazi flag, has come to symbolize Hitler and the Holocaust and Nazism, but this wasn't always so. The word "swastika" comes from Sanskrit (an ancient language of India) and means "good fortune" (source). The symbol itself is over five thousand years old. Due to its misuse by Hitler, it will be a long time, if ever, before it can be used effectively to positive ends.
Much of the novel's symbolism derives from the books it features. Check out Liesel's "Character Analysis" for lots of discussion on how these books comment symbolically on Liesel, and how book stealing functions as a symbol of resistance against the Nazi regime.
The book burning scene is important to Liesel, but symbolically, it goes beyond her story. First of all, it's a symbol of the countless other book burning in Nazi Germany. It's a bit of a reduction to call these events "book burnings." As the novel indicates, it's not only books being burned, but also art, pamphlets, anything authored by a Jew, or which speaks favorably about Jewish people.
These burnings don't target a single author, or even a single idea, but the collective body of creative and intellectual work of a large group of people. This goes beyond censorship or protest, and it goes beyond books. For the Nazis, Jewish books symbolize Jewish people. The destruction of these books symbolized their goals, the destruction of the Jewish people. The crematoria, chambers where the bodies of Jewish people were incinerated, are notorious. The book burning in the novel reminds us of those crematoria, and helps keep us from getting too comfortable in the story. It also reminds us that Nazi propaganda techniques included destroying information, as well as spreading it.
Death's fascination with the colors of the sky functions as imagery. It helps cast the mood of the story, and creates much of the atmosphere. By focusing on the sky-colors at the times of human deaths, Death suggests that there is a connection between a person's death and the natural world. The idea that each person dies with their own color of sky presents a vision of a universe which cares about humans, and isn't indifferent to them. For Death, the colors are also edible, and he sucks on them for distraction while he's on the job.