Silhouette

sil·hou·ette : the dark shape and outline of someone or something visible against a lighter background, especially in dim light.

There's a fascinating origin to the word (as I've learnt today).  It derives from the name of Étienne de Silhouette, a French finance minister who, in 1759, was forced by France's credit crisis during the Seven Years' War to impose severe economic demands upon the French people, particularly the wealthy.  Because of de Silhouette's austere economies, his name became synonymous with anything done or made cheaply and so with these outline portraits.  Prior to the advent of photography, silhouette profiles cut from black card were the cheapest way of recording a person's appearance.  Taken from this source.