I got inspired to invent my own national costume for a friend's made up country named Argosa. I used my own viking ancestry as a base idea and combined it with a gypsy style. (I'm from Denmark) The blue rose is a symbol of the country and the royal family because it's the only place in the world where the roses grow and where blue foxes originate. The royal family has been blue foxes for millennia and Jonathan's big sister Scorpia is the crown princess and next in line.
The half moon and flower on the sword is a religious symbol for the highest deity in their belief system.