I've always preferred top & bottom designs over side by sides. That was something that started in College, when I found out that a pizza box and other wide objects fit much better into a top & bottom. I prefer bottom freezers too, since I am into the fridge compartment more than the freezer, and I'd rather have the fridge at eye level.
Maytag has a neat door design out nowadays that has two small doors, instead of 1 large one. That way less cool air is spilled out when the door is opened.
The ultimate design for efficiency sake would be a chest refrigerator, that is accessed by the top. Cold air falls, so there is less a chance of it escaping out of the open top than it would be out of a door on the side of the box.
The location of the mechanical components have always baffled me. Most household refrigerators have the compressor and condenser located in the bottom. Heat rises, so the heat removed from the food compartments goes right back in them as it rises back through the bottom of the fridge.
One of the things that always annoyed me was the design of the condenser too. Most of the time, refrigerators have small condensers that use forced air from a fan to offset the smaller size. With the condenser located at the bottom of the fridge, and having air drawn over them also means that they will pick up all the other dirt, dust and debris hanging out at floor level. Installing a larger condenser across the back of the fridge, and eliminating the fan altogether is more expensive, but is more efficient. First, because you don't have the wattage of a fan being consumed, but also because the coils don't get dirty and dusty, and also because the heat is not being radiated back inside the fridge.
So, what's my "ultimate" fridge design? Well, I'd like a fridge with the compressor on top, like the professional models, and a condenser either on the back, or on top...and it has to be passively cooled, no consenser fans! It would be a "2-door"model. I don't need thru-door ice, but I don't have kids yet either. What I especially like though is stainless steel or chrome accents....it's a machine, let's celebrate that fact and make it look cool!