So I went ahead yesterday and stuck in walls for an enclosed shower and a little arch over the tub. Ignore the fact that the arch is very wonky. I will recut it later, after the tiles are glued in. The end wall of the shower is also not glued so I can tile inside the shower. Although now I don't think I'll have enough tiles. Anyway, I think I like it. As pointed out by Karin, there was a lack of height and focal points. I am a little worried that the shower/tub wall will overpower the left wall, but I think by the time the mirror is stuck to the wall with the shelf and other items, it will help balance it out. And Elizabeth's idea of a light in the tub enclosure is a good one too, especially as you'll get a view of it through the open doors from the front of the house (apologies to those who don't like their bathroom fixtures in full view of open doors!).
Really awesome stuff! And as for the Coxwolds, I sliced through the wallpaper on the shop wall and pulled that warped wall out. My husband helped me cut and glue some thin MDF to it and we weighted it down, so now it's flat and stuck back in the shop! Fortunately, as the wallpaper has a busy stripe pattern, the (rough) cut through the paper won't be very noticable once it's properly glued back down.
Happy mini-ing! I am off to paint the real life house....
PS I think I'll be sad to see the wallpaper in this room disappear. Perhaps I will purchase some more for a future project.