I would go very minimalist.

Maybe just the falcon being chased or rushing into battle, then just a small font at the bottom of Star Wars: The Force Awakens. Lots of empty space.

Or half of the crumpled up Vader mask on one side that fades into Kylo rens mask on the other. Stick a pair crossed lightsabers at the bottom being held by figures that we can't make out.

Or steal a bit of iconic imagery and have the new main cast jammed into the cockpit of the falcon with looks of distress.

There's so much hype, I think a very low key poster will get the audience even more frothed up.