You said dream barn, right? Well, my dreams can be pretty lofty. xD
I used a program called Google Sketchup to make my designs, but here's some labeled screenshots.
The general layout -- an indoor arena (100'x200'), attached to a barn area with twelve stalls.
And here's a close up on the barn area. The stalls are all 14'x14' -- my biggest current horse is a 16' gelding, but I hope to one day own a draft. I also figured that I would go with a larger stall for the rest of the horses, because 1) none of my horses, with the exception of possibly Tanner and Magic, have ever been stalled, so likely would not be used to it, and 2) It's better to have a stall that's too big than too small.
As for the feed/storage area... I'm dead set on having a separate, fireproofed building for hay, it's just a matter of if I want to keep all the feed there or not. I could also probably use the storage space.
The office has a window that opens to the arena, too.
And just an overall view of the entire building. I have the roof of the arena set as being semi-transparent, because I know I want it to be lit by mostly natural lighting, but I'm not sure if I want to go with one of those clearspan-type of buildings, or a lot of skylights, or what. There's also a large door on all three outside walls of the arena, that can be opened to allow airflow and such. (Could probably use it as a run-in, too.)
As for flooring, I'm torn between a textured mat, or textured cement like they have at my mom's workplace.
I warned you that I have lofty dreams.
We do plan on putting a barn up soon, but chances are, it will be a lot simpler than this. And won't have an indoor arena.