I was working on a boss room last night, however it was a bit of a mess. I made a new one tonight and I'm happy with how it turned out. It's a fairly compact boss room: 41X37
It looks to be in the shape of an hourglass (or an overturned 8 maybe?) The rise in the bottom middle is supposed to be like the shrine where some ancient artifact would stand on. (I was intending to put step slopes along the top ceiling too but it only works for the floor it seems)
Hopefully it'll work for all the bosses, I tested it a few times with the amoeba and skelebot but not with the dragon. (It's not big so it'll probably be fine.)