One motif you could talk about is death. You could focus on the lethal situation of Marjane. She faces the constant threat of death from both the external political environment and, in a way, from herself. In Vienna, she almost dies of bronchitis. When she returns to Iran, she tries to kill herself. You could also bring up Uncle Anoosh. Her beloved uncle is put to death by the Iranian government.
A good quote to illustrate the motif of death is “Nothing's worse than saying goodbye. It's a little like dying.” In Marjane’s case, a goodbye could mean death. She said goodbye to Iran and almost died in Vienna. When she said goodbye to Vienna, she almost died in Iran.
Another motif could be change. You could highlight how Marjane changes and develops throughout the two parts. Sometimes, the changes happen more internally, often brought about by her avid reading. Sometimes the changes are much more outward. She changes countries, the way she looks, and even some of her convictions. She uses drugs and alcohol when, previously, she was opposed to them.
A quote that illustrates the change motif might be when Marjane says, “If I wasn’t comfortable with myself, I would never be comfortable.” You could claim that Marjane’s constant change connects to her uncertain identity. You might say that it’s kind of hard for Marjane to keep things the same when her country of origin is suffering from deadly unrest while she’s also trying to adapt to a new way of life in Vienna.
A third motif involves independence. While Marjane changes throughout the graphic novel, I think it’s safe to say that Marjane’s will and self-sufficiency is rather constant. She has determination to educate herself, to protest, and to stand up for herself. When a nun demeans Iranians, Marjane calls her out even though it leads to her expulsion. Her will and independence is also on display when she’s able to survive in Vienna without a home.
A good quote that illustrates the ways in which Marjane stays faithful to her independent nature (even when it gets her in trouble) is when Marjane's grandma tells her, “Always keep your dignity and be true to yourself.” You could claim Marjane’s homelessness is an act of dignity. Rather than suffer the indignity of the thief accusation, Marjane chooses to live out on the streets.