Imaginative isn't my particularly my strong point and if you don't already have a template to go off, now's probably not the best time to think about going for this form but there's several ways. Firstly, decide if you want a direct link or not i.e. how explicit you want to be. Either write from the perspective of the characters and actually be part of Streetcar, writing a sequel, prequel, alternate ending or whatever, or write something which is totally independent and stay away from any explicit links. Don't go half way and write from the perspective of another character then say 'I feel like Blanche'. It feels very forced and ruins the flow of your piece. You could try and take some of the symbols, quotes or character traits from the story and parallel them in yours, but don't be overly explicit. Ultimately though, these are mostly just gimmicks if you use them on their own. The whole purpose of the texts is to use them to guide your ideas, and copying any of the characters, symbols, quotes and such are merely a vehicle for allowing you to more clearly represent such ideas within your own piece.