Aquascaping rock can be pretty cool. I like setting up a center piece in the tank and then build out from that.
I went down to our local stone yard and picked out two round river rocks that lay flat bout the same size. Then got a nice thick rock to lay across the river rocks to work as a stage. Then got a holy rock that looked interesting to be the center piece. Built it up right there to make sure it would be solid and stable.
I think it cost me about .40 to .50 cents p/pound. Try not to buy this at a LFS
as they will charge you like 3 dollars p/pound.
In my 55 Gal
I used the 'rule of thirds' and off centered the main piece.
You have some nice rocks, post up the final result.