^ I believe the key element to a successful 'little black dress' is relative simplicity in the design that allows the use of accessories au courant.
Here's what wikipedia has to say:
A little black dress is a short, unfussy evening or cocktail dress, popularized in the 1920s by the fashion designer Coco Chanel with her "Ford" dress, as Vogue later called it. Like the Henry Ford’s cars, it was an instant craze, widely available and, like the Model T, it came in only one color, black. Chanel's dress was designed to not show stains and to fit every woman. Coco believed that fashion should be functional.
The "little black dress" is considered by many women to be an essential part of a complete wardrobe. It is a well-known "rule of fashion" that every woman should own a simple, elegant black dress that can be dressed up or down depending on the occasion. For example, a simple black cocktail dress could be made into an evening dress with diamond accessories, stilettos and long gloves; or, when combined with a black suit jacket, demure accessories and simple pumps, the same dress could be worn to a daytime business meeting. Its ubiquity is such that many refer to it by acronym, LBD.
