Chivalry is set in a fictional version of Europe roughly set in the medieval times. It is grounded in reality and not overly fantasy-inspired. however elements from middle eastern culture and earlier European cultures do inspire certain elements of the game.
Anything that could plausibly be found in Europe/middle east up until the 1500's is fair game. These don't necessarily need to be replicas or period accurate items, as long as the design looks believable enough to fit into the style of the game.