Every culture has its armor and their armors always, without exception, fit in with the culture they belong to. Even more than weapons, armor makes or breaks a cultures feel and theme, you would not expect to see a Germanic Barbarian Wearing samurai armor, nor would you ever think of seeing Native Americans wearing Aztec wear.
Needless to say the armor a culture wears is are as important as their beliefs and necessary to keep the feel of that culture and many works of fantasy show great design that fits the feel of their armor; such as the Thalmors armor in Skyrim, or the Orcish armor in Lord of the Rings. What things should you keep in mind when designing cultural armor?