Good question! It needs to be unmarred, unblemished, unstained. But if it were perfectly symmetrical (like, say, a formal French garden) it would look a little weird. So, maybe it can have some of that, and some of the Valar working together and allowing their own spheres to interact?
I don't know that it needs to feature too much symmetry; one of the things that we did in the first episode was encourage the audience to see the Valar as being a little more "human" by having them prefer the more natural-looking landscape created by Osse's constant pounding of the originally blocky coastal cliffs over their inital, other-worldly look. I think there should be some very obvious symmetry, but I'd like to see some of the features looking a little more natural; they're not just building up layers on top of each other, they're making an honest to goodness stab at this harmony thing. We could look to fractals as a visual basis to help us with that, gesturing at patterns and order while still being pretty organic.