When I saw Brave, I noticed that the Queen’s dress reminded me a lot of Sargent’s painting of Ellen Terry as Lady Macbeth. When I got home and looked up pictures of it, there was no doubt in my mind that it was inspired by the dress. It’s almost exact. Even her hair is the same.
Edit: Wow! So many notes! Thanks guys! Also, some people seem to be concerned about possible connections between the two characters. I assure you, the similarities between Lady Macbeth and Queen Elinor pretty much stop at the dress. ;)