One of the larger features that we're really excited about is the Terrain (Landscape) Editor. This a big part of the upcoming update and will allow players to create their own worlds.
You can build your own realm, fill it with your drawings, and watch it come to life. You can then share your world and dive into your weird and wonderful creations with friends.
We're looking forward to seeing the kinds of creative worlds players create. You can catch more shots of the editor in action in this (already shared) video: https://www.youtube.com/watch?v=70JzKIO6YlQ