If tattoos were going to be a problem for a Moslem, it was usually upon admission to paradise. This ceased to be a concern if the wearer was sure he would be purified by fire before entry. "Tattoo? What tattoo?" Bans notwithstanding, tattoos are simply too attractive when it comes to expressing something as fundamental as one's beliefs.
For Moslems, their first choices are usually the Crescent with Star - although originally a political symbol, or verses of the Koran, usually in Arabic calligraphy, or the Hand of Fatima. In Islam, which overlaps with Christianity, Angels, Satan, and even Adam and Eve are also meaningful symbols.