After Diana and Steve leave Themyscira, we don’t see any of the other Amazons again. This is both a feature (since it lets Diana grow as a person and a heroine) and a bug (because the Amazons are pretty cool).
Granted, they’re all stuck on Themyscira, but who’s to say that Diana hasn’t made the trip home at one point or another in the ensuing century between first leaving and when we see her at the Louvre? Maybe she makes regular visits.
Regardless, we’d like to see more of her relationship with her mother, Hippolyta, explored in the next film. It’s clear the two of them love each other deeply, and they could likely find a lot more common ground now that Diana’s had some real experiences in man’s world. I want to see them reconcile — and yes, perhaps a little tension over the fact that Diana didn’t know that she herself was the God Killer all along. What other secrets could Hippolyta be hiding? What does she know about what Diana might be capable of?
These are the kinds of things that could really help fuel a second film without feeling too much like a rehash of the first. Wonder Woman had a lot to do with the idea of discovery; more of the truth coming out would make for a natural extension. After all, the Lasso of Truth is still part of Diana’s arsenal.