Tank looks like it is coming along nicely.
I have a few suggestions, one is on the flow you asre using. I would add a couple powerheads in the tank, the 300gph pump you are using for the return is quite underpowered. I would strive to have about 1000-2000gph in the tank depending on what you are looking to keep for corals. If you are going to do a fish only, I would still increase it toward the lower end of that range.
Before you get too far in I would also consider using a sand type of substrate rather than crushed coral. Crushed coral being so big and irregularly shaped tends to trap a lot of detritus and make for a dirtier tank. Aklso makes it difficult if you want any sand sifting, burrowing, or fish that sleep in the sand in the future.
And lastly I would consider building a box for the overflow out of black acrylic and paint the back of the tank to help it all kind of disapear into the background.
Just a few thoughts.