I love the asteroid.
I would love to see more of 'em.
The moon near the water world is a bit flat, will you make it a bit more boxy?
Also, a volcano like bit on the lava world would be nice.
EDIT: I checked out the save and there are some odd things i would like to point out:
First of all, water world:

You cannot see everything, but:
1. Water does not cover everything, on the picture you can see an open spot where there is no water currently.
2.Ugly water lines in water, you placed different water bricks on eachother which causes that there is a water line underwater.
Not very attracting. :C
Then in the lava world, the lava is made out of normal blocks.
While i understand that this is looking water for waterfalls and is easier to event with default events, i must say that when looking from inside the cave, the waterfall doesn't really looks nice.
However, it looks better than my version of an environment for the lava world as i just use emitters for the waterfall. :C
(I also added ambient lights to my waterbricks as it gives the really hot lava feeling. But it doesn't always show up nicely. :S)
But there are some points in which it doesn't really appeal to me. :)