Most books and articles on the web that I've read say to pile it high in the middle in any weird funky but stable assortment that you find attractive. Keep it off the glass, all four sides and if you have a good quality, perhaps Fiji rock there will be lots of 'natural' hidding places for your fish. That's what I read. As for my tank, it's all piled up along the back wall and along one of the sides. It looks great, to me, and there are many cavernous caves. It also hides most of the plumbing and I don't mind the algae growth on the back and side wall, adds character and it's really not too bad.
My suggestion, do what you think looks nice. You can always rearange it before you add any live-stock.
I have approx. 90lbs in a 65 gallon, looks nice.
If you go with the centre pile, you need more ro ck to achieve the desired height. If you pile high along the back, you can get away with less rock.