I would love to see some pictures of the rest of the area. I love midcentury and am doing a 1948 post war right now. Doing it midcentury.

based on the drawing, the wall where the bed is. HOWEVER, you mentioned that this drawing is not a true depiction of the furniture you will use and the wallpaper. if that is the case, i think the wall paper can work on either wall, it all depends on how busy this wallpaper is and how "plain" the bed is. if you go with a busy wallpaper behind the bed, you may want to keep your bed and bedding on the minimal side so that there is a good visual balance to the overall composition. if you go with snazzier bedroom furniture, then a busy wallpaper may be a bit much and you may want to put it on the other wall or use a textural option to serve as the bed's background rather then another focal point.

We make self-adhesive fabric wallpaper that is great for feature walls - and you can install it yourself! :)

Yes, I had noticed a lot of pics on Houzz, that's what gave me the idea! I certainly wouldn't put it IN the shower! We have a tiled shower, but the tiles only go as high as the glass surrounds, so there is about 30cm of painted wall above the shower, which is the part I was worried about with steam etc.