That's my single tier brewstand, mostly built from several Home Depot trips. I'm not really satisified with it though. The casters I put on it were too small, so it's a pain to move around. I also discovered that putting 6 caster wheels was pointless unless the weight is distributed to the wheels evenly in the middle. If you put wheels in the center of the frame they just act as a pivot point when trying to roll your stand around. I will remove my middle wheels if I decide to upgrade to bigger casters, but then I have to consider weight again, and wonder how much weight the slotted steel frame can support.
As far as dimensions go, and I speak only to single tier stands, there are some simple rules that should be followed in my opinion:
The stand should be not much wider than 30". This will allow it to be rolled through 99% of all doorways, even the smaller 32" doors, without removing the door (or screen) from it's hinge.
The stand should not be taller than 7' including side casters, for rolling the stand on it's long side, again, to fit through doorways and for small footprint storage.
The main advantage in single tier is eliminating the need for step stools or ladders, so keep the kettle openings low enough for the average brewer to be able to see in is key. If you have a single tier stand and still use a step stool to look in, you're either really short or your stand was built improperly.
I'm not sure why, but I see most brew stands, both gas and electric, seem to be open framed. When I built mine it was intended for 3 burners. I still wanted the steel grate on it for the ability to set things on the top without worry of them falling through the frame. I also added the steel grate underneath so I could easily store things underneath. I was a little worried about heat dissipation but quickly found out the heat traveled through the steel only a few inches. The grate acted as a huge heat sink as air travelled around it. A huge mistake was not quickly painting the grate with high temp paint, now it's very "rustic".
Now that I am all electric the grate is even more appreciated since I have no heat transfer at all. I can set a glass of cold beer next to BK and have no worries.
I've been contemplating a badass stand lately because I want the strength and durability of square welds. I have yet to request a quote though because I'd have to have it customized with a control panel arm, I'd want a grate on top and bottom again for the same reasons, a mash dump, and an arm on the opposite side that would serve as hooks to store hoses, utensils, etc.