Good ideas! How about the contradictions between Amanda as an old-fashioned Southern belle and as a modern woman. The Southern belle part is easy because its so rather ridiculous. She adopts an accent, puts on the dress from her days as a debutante, flirts outrageously with Jim...and more. On the other side, though, are some issues which may get overlooked in the "bigness" of her personality. She's a single mother who's raised two kids, holds two jobs, provides for her family--all things which were not especially typical of women in the mid-1900s. Just something to think about.
Exploring the concept of illusion versus reality might also be a good topic to explore. Since Laura, as stated above, lives in a world surrounded by her glass animals and her protective nature, she has shut herself off from the pains of the real world. Similarly, Tom dreams of having a life outside his current situation, but he just assumes that some other life would actually be better than the one he currently has.
There are literally hundreds of topics one could write about pertaining to this play. If I could choose any topic, I would do a paper about the strained family dynamic between Tom, Laura, and Amanda and how they meet and do not meet traditional family roles.
Considering that Tennessee Williams wrote this play with the setting in 1944, the topic of comparing and contrasting the roles of Mother, Son, and daughter would be a good direction to go. The culture during that era was very different than the culture today. The son was expected to take care of the family after the departure of his father. The women are portrayed as weak and fragile characters.
If you don't like that idea you might analyze the personalities of the three main characters and how they use fantasy to escape the harsh reality of their lives. The mother dreams of days gone by, the daughter lives through her glass animals, and the son dreams of escaping through the merchant marines. A great deal of material on the specifics of setting, symbols, and theme can be found at the link listed below.
The theme of isolation is definitely present here... All of the family is completely isolated despite living together. Although Laura lives in a world of glass animals, Tom and Amanda also live in their own little world. Amanda still lives in Blue Mountain and can only recall the days when she was popular. Tom wishes to break out of the house and join the merchant marines. It's funny how people can live under one roof and still remain so closed off. Plus, the entire play takes place in the apartment. This also shows how their lives are limited to one place. The dance hall across the street offers excitement and represents the outside world, but no one bothers to notice (except Jim).