Different symbols relate to different themes, I believe.
For example, the glass menagerie relates to the theme of social outcasts. One of Tennessee Williams' favorite themes is what is society's obligation to societal misfits? Laura represents this clearly, and her disappearance into the world of her crystal animals is symbolic of her inability to live in the real world. When the unicorn's horn breaks off, she contends that it will be happier as it won't feel so "freakish" anymore. Williams poses the question as to whether people who are different should change to be the same or whether there is a place in society for these different folks. Another symbol that relates to this theme is the Victrola. Amanda accuses Laura of using the Victrola as a way of avoiding reality.
Another theme you might consider is the theme of the past. The old fashioned dress Amanda puts on for Jim's visit is symbolic of her inability to deal with the present. She is more interested in reliving the glory of her youth when she was inundated with gentlemen callers. Another symbol that relates to this theme is the portrait of the father. The portrait dominates the apartment, and his lack of physical presence is romanticized - a "telephone man who fell in love with long distance." It is also a constant reminder to Tom that he is now responsible for Amanda and Laura.
There are more, but I'm out of room!
The Glass Menagerie contains many symbols, for example, the glass animals that Laura keeps are symbolic of her own fragile nature, both physically and emotionally. Disappointment and disallusionment are two themes that run through the play. Laura is distracted by her interest in the fake world that she enjoys as she polishes her glass animals. Too afraid to mix in the real world, afraid of rejection or criticism, or failure.
The apartment's closeness to the dance hall is symbolic of the Wingfield's being just on the edge of real happiness in life, but never included. This ties in with the surreal quality that exists in the Wingfields apartment, not quite reality, but a dream-like hell for the characters, one that they cannot wake from.
The lights going out during the dinner with the gentleman caller, Jim, is symbolic of the darkness that will descend on the family, since Tom has decided to abandon the family, just like his father so many years before. Appearances vs. reality, the family almost looks normal, but underneath the appearance, the reality is very different.
Blue Roses, Jim's high school name for Laura is symbolic of how different she is from other girls. Not red like most roses, or pink or white or yellow, but blue, also relevant to the way that she feels, and how she will be disappointed by Jim. Appearances vs. reality again, Laura is not really that different from other girls.
The fire escape symbolically provides the only relief that Tom can get from the frustration that he feels with his mother. Like a tool used to run from real fires, the fire escape allows Tom breathing room when things get too heated inside the apartment. Escape is a theme that is consistent with the character of Tom, who longs to leave his life in the apartment behind.