What types of imagery are used in A Streetcar Named Desire, and what do they mean?

One of the most important images of the play is the paper lantern that Blanche buys. Blanche "can't stand a naked light bulb" because she is so self-conscious about her aging beauty. She needs the lantern to cover the bulb and diminish the light, so that she looks, in the half-light, "soft and attractive." As she says to Stella, "You've got to be soft and attractive. And I - I'm fading now! I don't know how much longer I can turn the trick." On a deeper level, the image of the lantern over the light also represents more broadly Blanche's desire to hide her past. She wants to appear chaste and respectable, like a traditional Southern belle, but this is a fading facade which hides a more sordid reality of promiscuity and alcoholism. Towards the end of the play, Mitch tears the lantern from the bulb, declaring, "I've never had a real good look at you," and in so doing he exposes Blanche physically, but more importantly he also exposes (to the literal and metaphorical light) her past, and her true character.
Another key image, from the final scene, is the image of the "grotesque" shadows and "lurid reflections" that appear on the walls around Blanche, and that begin to "move sinuously as flames." These images of sinuous shadows and reflections accompany and visually represent Blanche's mental breakdown. They are the reflections and shadows from her past which haunt her. In this same scene, the walls of the stage become transparent, representing how, for Blanche, the barriers between reality and fiction, past and present, and madness and sanity, have all finally broken down.
A third key image, from the opening scene of the play, is the package of meat that Stanley "heaves" towards Stella. This is a significant image because it places Stanley as a primitive, caveman type of character. He is the alpha male, bringing the meat home for his woman. The primitive impression is compounded by Stanley's monosyllabic utterances of "Catch!" and "Meat!"

Flower imagery is common in A Streetcar Named Desire. The flowers represent both youth and decay. In scene 3, Stella calls Blanche "fresh as a daisy," to which Blanche responds she's a daisy that's been plucked a few days.
In scene 9, Blanche hears a woman in the street selling flowers for the dead. This reminds her of the family she has lost and hammers home her reminder of her own mortality. As a result, the woman's calls make her hysterical.
Light and darkness play a big role as well. Light represents reality, the very thing Blanche wants to avoid, while darkness represents fantasy and hiding from the truth. She covers bare bulbs in paper lanterns and tries to stay in the shadows to hide her age. She is terrified of the truth of her life: she is no longer a young, pure southern belle, but an alcoholic woman of thirty.