The patterns on their uniforms signified their rank or type of soldier they were. You can see the joins where they have been put back together as the majority had been damaged prior to being found. As the pieces are unearthed they are numbered and the numbers signify which area they were found in.  The completed figures can then be placed back where they were found, once they are satisfied that all usable pieces have been used. These were standing together at the end of pit one waiting to be placed back.

No warrior has the same face and were modeled from real people, as the emperor wanted a realistic army in the afterlife. It is said that once the workers had exhausted their supply of faces they then started to mix and match using different elements of the already completed figures. The emperor also  ensured that the figures  were just over average height so he had a super army to protect him.