On the topic, I think it is good to create a world where things have a reason behind it without passing off the familiar as logical. This creates a more immerse world. I think the main issue would be making sure you are not striving for realism. You can create a new world. Why have it follow the rules of this world? One of my favorite games, Xenoblade, does this pretty well in my opinion. http://www.youtube.com/watch?v=84Y95Uu6vng It has glowing trees, floating islands, and the game itself takes place on two titans. The examples you gave seems to follow the logic of our world, but this is what I think you are actually getting at and that is moving away from the familiar.
I don't know if that made any sense since I'm far too sleepy.







