plaque

noun

1. any thin, flat piece of metal, wood, etc., with a picture, design in relief, etc., hung as on a wall for ornamentation
2. a wall tablet inscribed to commemorate an event, identify a building, etc.
a platelike brooch worn as a badge or ornament
1. an abnormal patch on the skin, mucous membrane, etc.
2. a thin, transparent film on a tooth surface, containing mucin, bacteria, etc.: if not removed it forms tartar and promotes tooth decay
3. a deposit of fatty or fibrous material in a blood vessel wall

See plaque in American Heritage Dictionary 4