Favorite type of zone: honestly, something like Mor Dhona or Coerthas (though I get the feeling I'd like them even better if I could turn off the cut-out looking minimap), but with a bit more to do.

I'd like to see some temple ruins in the Black Shroud, preferably surrounded by the current Black Shroud appearance. Within places that are equally labyrinth-like, I'd really enjoy it if the zones were made just a little more pathable (little places you could pull yourself up or jump onto and go through a small otherwise hidden path). Generally more things that retain its feel as a labyrinth but don't have you running 200 yalms just to move over 50 all the time. Add complexity, but a bit less irritation.

In Thanalan, more diversity, and I really want something a little more... sandy. The arid look feels nicely real, but plenty of other types of scenery can do the same while lending some variance.

Snowy zones would be great. Some small islands off the shore of Limsa would also be great. Underwater ruins, wonderful.