Alright, so having played with this mod for quite a bit, and generated several worlds to test it, I have a few points that hopefully will help you improve this mod.
Firstly, the world appears empty. With this I do not mean the empty space between, which is fine to me (though, a few smaller islands could be cool), but the islands itself. There are basically no landmarks to populate the world is what I notice, and perhaps a thing you could do, is create landmark islands. Islands that are basically solely meant for existing, or your own landmarks, and worked into it. (I hope you get what I mean with this xD)
Secondly, water. For what I noticed, there is simply no water to be spawned, which is sad because I think it would look really cool, especiall if that water could fall down and create an ‘endless’ waterfall (though I would recommend making sure the water stops at the bottom of the world, and not continue as that may cause problems).
Thirdly, due to the fact there is void, building over this void (for example, giant bridges), could become tricky and you’ll often have to cheat them in. This, of course, isn’t really your problem, though putting down a disclaimer may help a bit.
I hope this helps a bit!