One of the methods early nomadic groups used to tattoo variations of the Greek cross, a cross which consisted of arms of equal length, was by taking a needle and thread dipped in an ink solution and would literally sew the image of the tattoo into the skin leaving the ink behind. There are very few people in the modern world who know how to perform such tattoos in a safe, sanitary, and historically accurate way. If you watch the show “Taboo” and happen to catch the episode about tattoos then you’ll know what I’m talking about.
Even though they play a major role in the symbolism of different empires, cultures, etc the modern cross is mostly associated with Christianity and the crucifixion of Jesus as stated in the New Testament. There are many types of crosses that one would want to use to express their religious meaning. The first, as mentioned above, would be the Latin cross. The Latin cross is one of the most identifiable and common types of crosses used by almost every branch of Christianity. This type of cross is easily recognizable, widely accepted, and can be altered by using ones imagination. It typically consists of a vertical line intersected at right angles by a shorter horizontal line. In order to express ones religious devotion they can add a dove, some olives, a portrait of someone they love or a lost loved one. This cross tattoo has so many options and alterations they are endless. Another type of cross would be the Celtic cross because it symbolizes the never ending nature of human life. The Celtic cross is similar to the Christian cross but it has a Celtic knot that is placed over the area where both the lines of the cross intersect. It is simple and elegant and very unique, especially in the states. I would imagine this type of cross tattoo is found more in the United Kingdom area. Another religious cross would be St. Andrews Cross which is shaped more like an “X” instead of a “T”. People of Scottish descent particularly enjoy this one to show off their heritage.
In addition to all of these there are multiple types of non religious crosses that can be used like the Egyptian Ankh symbolizing infinity and fertility, the Gothic Cross influenced by the Edwardian Gothic period, and finally the Tau Cross.