Welcome to reefkeeping - where a bunch of guys debate the best way to pile of bunch of expensive rocks.
My advice on aquascaping is
* Less is more - I think tanks with less piles of rocks look better and allow you to see through the tank.
* Create some caves and paths for the fish to swim through - this allows you to see through the rock which adds depth and interest to the tank as well as creating movement with the fish (they swim through and around rather than back and forth).
* Horizontal space is more important than vertical space - When it comes to placing corals it is better to have ledges and flat spots at all vertical levels so the corals have a place to sit and grow..
* Make it stable - yours looks like it could easily topple over. Doesn't seem like a big deal but you'll constantly be wanting to relocate corals or remove them from the tank and risk bumping something and causing a rock slide.
* Don't overthink it - get a basic aquascape together and let the corals grow and hide the rock. Once you get good growth you almost don't notice what type of rock you have.
* Do what looks best to YOU.
-Mike