There's really not anything I could tell you to make all of this stuff look the way you want it. I find that the best thing to do when you don't know how to draw something, is to go outside and observe the real thing or find pictures and videos on the internet. Obviously you can't go look at floating cities in real life, but you can look at clouds, water, water falls, grass, people, buildings, etc. You might also find some useful things here. http://conceptart.org/forums/showthr...ee-Art-E-Books
Best of luck!