Love Kate's earrings (which we can finally see, on the carriage ride)!
I love that they're small, so you aren't distracted. They're also a good match with the neckline of her dress; since the collar comes up past her collarbone, it's best not to have something that interferes.
I love that they're drops, so they swing and twinkle as she moves. They also help emphasize her neck.