Miranda's office bears some strong similarities to the real office of editor-in-chief, Anna Wintour, down to an octagonal mirror on the wall, photographs and a floral arrangement on the desk. The movie magazine Runway is very similar to Vogue.
Here is a great picture I found that shows the comparison of the two offices together.
Her office was designed by Cathy Whitlock and mentioned in her book, Designs of Film. Many fans of The Devil Wears Prada have taken the inspiration from Miranda's office and have transformed their spare rooms into their personal offices. Everyone that has watched this movie, has taken a part of it with them - transforming themselves in one form or another.
I also found two pictures that show the entire layout of Miranda's Office.