This doesn't actually need to be a boss room (but it works very well as one), except it has tons of crates (being a storeroom and all) and I think it was mentioned that crates shouldn't be outside boss rooms that much.
This room is 26X71, I wanted to make something large but still a bit compact. So there's the best of both worlds in this one.
The boss will nearly always appear in the bottom half (there are a couple of areas above where amoebas and dragons might spawn...and even then the dragon will usually fall below through the bridge) so it means after the fight is done it's worth exploring the rest of the storeroom. I came across an exp container while I was testing it. (along with the usual items, monster spawners and doors work fine)
Plus there's at least one 8X8 surface in this one (it doesn't matter if that surface is crates does it?)