Geist700, the worlds are finite. If you go too far away from 0,0,0 (the centre of the world) you will get to unplayable areas such as below:
In reality, without using the teleport command you would probably never get this far out from 0,0,0. Unless your mission over the next couple of years is to try walking and boating this distance. ![]()
Having said that, the playable area is pretty big (maybe that is an understatement) - the world is procedurally generated using the inputted seed from the center of the world (0,0,0).
Because of this you can't see a preview because the world has not been generated yet.
Personally, I wouldn't worry about getting a preview, the islands in Rising World are exceptionally diverse. And at the end of the day they all use the same procedural generation!