The Boy in the Striped Pyjamas essay, can someone help me please?

I've done a paragraph on the character development of Bruno, and I'm going to explain his move from innocence to experience later on by explaining what happened at the end of the book. However, now I've to do a paragraph on symbolism and I really have no idea what to write. If someone could just give me an idea I can work with, I'm not asking you to do it for me but I could really use a bit of help with starting off. Thanks very much