What is a good symbol to represent Aunt Alexandra? Can Scout and Jem be represented by the mockingbird? What else is a good symbol for them?
It would be an odd symbol, but I'd use a nice tray with cookies on it for Aunt Alexandra. This would symbolize her ability to be a civilized lady and a model for Scout, even in the midst of the hatred and stupidity after Tom's death.
As for Jem and Scout, I guess you could use the mockingbird, but I wouldn't. I'd use a cut flower from Mrs. Dubose's camellia bushes. Both of the kids are involved in some way, and it shows several sides of their lives: the impulsiveness, the lessons learned, Atticus' role, etc.