Designs and Origins
Over the 2500 years of its existence, the art of rug-making has produced a seemingly endless variety of designs. In ancient times, the weaver would often take religious symbols or tales of heroic deeds as the subject matter of his work. Other more purely decorative motifs became closely associated with a particular tribe or region. The names of cities like Kashan, Tabriz and Agra have become indelibly associated with designs that are recognized as classic rug styles throughout the world. A tribal design like Bakhtiari is likewise synonymous with an entire tradition of rug-making that is characterized by a repeated diamond element.
As time went on, the unceasing activity of cross-continental nomads and traders caused designs to evolve into an ever-broadening array of motifs, continually overlapping and borrowing from each other. When European traders brought the first Persian carpets back to the royal courts of the Continent, the rich and powerful were quick to adopt these exquisite creations as one of the signature features of aristocratic life. Louis XIII was so enamored of the art form that he ordered the formation of the Ecóle Savonnerie to advance the technique of fine weaving in France. From this point, Europeans naturally began to develop their own design motifs, interpreting and expanding upon the Persian and Chinese designs of the original imports.
As the 20th century dawned, weavers from Europe to China began to experiment with more innovative design—from the Arts & Crafts Movement to Chinese Art Deco, to the leading edge contemporary styles.
From: http://www.nourison.com/NU/7design.asp