Dunno if this has already been brought up or not, pretty big thread.
The costuming reminds me of medieval Europe (Kylo looks very monk-like, the hilt swings him closer to feudal knight and away from feudal samurai). This makes me think the story draws from post-roman empire history for inspiration of what happened over the last 30 years. The first order may be more of a sith-based religious group, and they are in the middle of their own crusade for sith/jedi artifacts like Luke's lightsaber and Vaders helmet.
Although I do think that is Luke in the trailer looking at his fathers helmet, but that's just a hunch.