Rock scaping is a personal preference type of thing. One person might like a tight stack in the middle of the tank, another might like the entire back wall covered and even another might like a few pieces scattered here and there.
Personally I like cliffs, overhangs and caves. Places for fish to hide but not tightly stacked rocks. I also like more than one structure if there's room in the tank.
Like it was said before, at the end of the day you are the one that has to be happy with it.