Iranian weavers created and developed many decorative designs, with predominance of fine and intricate arabesques that constitute the backdrop for opulent medallions, palmettes, other abstract decorative elements or realistic flower and animal motifs. Most Persian rugs are square due to having been made on traditional looms. The fact that Persia was under the influence of Shiite Islam, much more liberal than the Anatolian Sunni doctrine, gave its weavers greater freedom of artistic expression, allowing them to create images of humans, which was strictly forbidden in other Islamic countries. From the 19th century onwards, representations of human figures even started to dominate Oriental rug designs. Color palettes are very rich and diverse but never too gaudy or contrasting. Usually, there are no extensive monocromatic fields. Colors are placed separately, often outlined with black, arranged into a harmonious whole with great panache. Red and blue as well as the combination of light motifs against the dark background tend to prevail. Naturally, the colors of rugs coming from nomadic tribes are far less subtle. Traditionally, weavers worked with the asymmetric knot, known as the Persian knot or Senneh. However, the symmetric knot, known as the Turkish or Ghiordes, was also applied in some regions. The weavers used wool, cotton, silk, and threads of gold and silver for the most luxurious carpets. Persian rugs range from small nomadic or village rugs to very large palatial and urban carpets. The most classic compositional scheme consists of a medallion in the center surrounded by arabesques or a pattern of botanical motifs.