A big part of the show revolves around the prince being taken to a fallen city (which is implied to have been something fantastic at some point in the past). Presumably, something happened there to cause the city's current state of disarray.
Various things (including Willow's flamethrower, and the armor pieces described by Boorman) indicate varying levels of technology being available. Disparate scraps of tech gives the impression that different areas of the world may have access to relics from a more-advanced past.
I'm not sure if the "Shattered Sea" actually means water. At first I thought that was the case, but some of how things have been described could be understood to mean some sort of wasteland (possibly radiated or ruined in some way).
As more details emerge about Elora Danan and what exactly Bavmorda was trying to do -notably banishing her soul- the more it vaguely resembles the background fluff for Warhammer's God-Emperor and how evil forces were trying to purge his soul.
Overall, it comes across as starting to feel more like there are touches of sci-fi or a post-apocalyptic setting. Though, in terms of being post-apocalyptic, the world isn't ruined. Enough time has passed that there is still a functioning world and society, but things from a previous age linger on.
The denim and graphic-print band tees also stand out as not quite fitting into fantasy.