I completely designed the tank myself, hoping to get as much of a unidirectional flow as possible.
This is a rough sketch of how its going turn out.

The tank measures 120x32x24 and will rest on a 36" high steel stand. The back is black acrylic.
Here are pics of the tank at the acrylic shop -
This pic shows the left side of the tank where the returns will be, 4 - 2" holes for the closed loop and the holes on top are for the returns from the sump.

This pic shows the overflow on the back right side. The overflow is actually going to be built on the outside of the tank. This will feed my sump.

This pic shows the right side of the tank, which will basically be one giant overflow. The Box with the drains will be on the outside of the tank as well. This will be a closed loop system feeding the returns on the outside of the tank. I will probably be putting a bead filter here , I also need to decide on which pumps to use.

Not shown in the pictures will be 4 closed loops holes drilled in the bottom to power 2 - Eheim 2260's or 2 Fluval FX5's, havent decided which yet.
I will be using sand or sand like material. I'm leaning towards a mix of black and white 3M Colorquartz. I hear a mix of black and white brings out the best colors.
This tank is mainly for my clowns, of which I have about 45. I also have striatas, yoyo's, darios, angelicus and schisturas. I will probably have some histronica also. I will be using Puntius Demasoni , Rainbow fish and maybe some sort of Tetra or barb as dither fish.
The decor will be alot of river rock, driftwood and slate.
More to Come! I plan on starting my build as soon as the tank arrives.