Footprint Muhammad and the Toeprint Caliphs
Conceptually this is my favorite. Muhammad (Mohammed) is the big toe. The others are the first 4 caliphs, the Rashidun or the so-called "rightly guilded" caliphs. The footprint itself is green which is supposed to be the color is Islam.
Blue is Abu Bakr, father of Muhammad's wife A'ishah. He ruled as caliph for two years.
Orange is Umar. He was assassinated by a Persian slave in 644.
Purple is Uthman. He married 2 of Muhammad's daughters. He was also murdered in office.
Red is Ali, Muhammad's son-in-law and cousin. He too was assassinated.