Currently my herp room is a spare bedroom, with one window, too few outlets, a bathroom too far away, and carpet.
So I've definitely spent time thinking about what I would change.

No carpet of course, and I'd love a big laundry sink with an extendable hose/tap fixture thing.

I'd definitely put in a comfy chair or two - currently we barely have any space to spend time with our animals either.

I would probably do a wall of stacking enclosures, large ones for boas and smaller ones for geckos. Another wall would be snake racks. Maybe 2 walls.

I'd like to build a couple of large boa enclosures into the living room wall as well, but that's a whole other story.