Sokka mentions to Princess Yue that in his tribe, he is "kinda like a Prince myself." Katara scoffs and makes fun of him. Considering that their father is the Chief of the Southern Water Tribe, it would be correct to assume that Sokka and Katara should be regarded as a Prince and Princess, respectively.
The martial-art style that waterbending is based off of is T'ai chi ch'uan, specifically the Yang style.
According to The Art of the Animated Series, the water chambers shown when the kids first arrive at the North Pole were inspired by the Panama Canal, and the waterways were inspired by the city of Venice, Italy.
The Art book states that the buildings at the North Pole are constructed with whale bones, and the ice is then built around them.
Zuko's crewman is shown playing a pipa or Chinese lute.