Dr. Muzammil H. Siddiqi, former President of the Islamic Society of North America, states: “Prophet Muhammad (peace and blessings be upon him) forbade his followers to make the images of living beings whether human or animals. The images of pious and religious figures were often worshiped by many people in Arabia as well as in other cultures and societies. Prophet Muhammad (peace and blessings be upon him) was very conscious that these images lead to idolatry. He always wanted to remind his followers to keep their faith in Allah pure from any idolatry or image worship.
It is for this reason that we do not have any picturial image of the Prophet (peace and blessings be upon him), but we have a lot of details available about his personality, appearance and his character. There is a whole genre of literature that is known as “Shama’il an-Nabi“, which means the physical appearance of the Prophet (peace and blessings be upon him). The companions of the Prophet have given us a full verbal description, so you can look at some of those books to satisfy your curiousity in this matter.”