Now on topic.. This is an excellent post, and I have a thing that I think should be considered:
Don't do giant cobble boxes. I'm sorry but they are ugly, also, I know that all of you can do better than that, luckily I haven't seen any giant cobble structures so far, yet I fear that they may appear one day. On the same topic, floaty planes of wood, cobble, dirt or other stuff ain't pretty either, if you want to do a floating island make it look like it was torn out of the earth, or put propellers or a giant balloon on it, makes the whole illusion so much better! Think about your builds and try and get some good inspiration, in that way we'll soon be playing on the prettiest server out there!
This topic is not about personal preference. People are free to build whatever they want (unless it's offensive), including ugly, cobblestone monstrosities.