If you have the resources, I suggest checking out some old magazines for inspiration. Perhaps your local library has some. If so, Vogue, Mademoiselle, Life, and Look are some great places to start. Notice the colors - pastels and metalics, and lines - clean and angular. Also, keep in mind that the 50s was all about "new" products, convienence, technology, science, and optimism.
Don't forget to add some kitch! Typical "themes" were tropical (Cuba was a popular place to go for vacation - maybe you can score some old-fashioned travel posters...I think Pottery Barn has some reproductions) and western (howdy-doody, Davey Crockett, etc.)
I hope that gives you a place to start. Also, here's a site that might be useful to you:
circa1950 Good luck, and let us know how it goes!
PS - Can you tell I was a history major, and I LOVE design??