2011's memorable and not so memorable nominees included (if you need a refresher): The Artist, The Descendants, Extremely Loud and Incredibly Close, The Help, Hugo, Midnight in Paris, Moneyball, The Tree of Life, and War Horse.
Now, some of these films have some worthy costuming associated with their unique period piece (I think of Hugo, The Help, and War Horse, here...maybe even Midnight in Paris), but there's no recognizable character or costume that can be simply captured. Sure dress up as a 1960s southern housewife, or a WWI soldier, but don't expect people to know you're dressed up as Cecilia Foote from the Help or a character from War Horse.
For Men & Women:
If you feel compelled to truly master a character and film from this list, it seems to me the best bet is to make your best attempt at the artist, capturing the look and feel of a silent movie star, and more specifically George Valentin (Jean Dujardin) or Peppy Miller (Berenice Bejo).
For the Brave, Daring, and Man (or Woman) Among People Who Would Appreciate It...
But if all of this talk of portraying the leads from The Artist, I really only have one other suggestion from the list of 9 films mentioned above.and that would be to dress as the automaton from the film Hugo. If you give this one a try, send me a picture and good luck.
Beyond those suggestions, I've got nothing. You might just have to dress up as Batman, again.