Im not sure how much brick is seen around the window frame, if its only a little brick, you could paint it, although I'd prefer it be a smooth rendered finishor plaster like your other finished walls, because if there are three surfaces visible in there, none will be a feature, and all will look incohessive. To let the ply wall take the focus the plaster is perfect in contrast, so if absolutely necessary, pair. He brick white, although my recommendation is to gy rock and paint, just with he back wall in marine ply. Good luck, I'd love to see your finished result. By the wY, mentioned split battens to hang the ply, if you're unfamiliar, it's where timber battens are cut in half on the diagonal through section, and one half is fixed to the wall, the other the ply sheet, when they go together they become a secure locking fixing. Any handy person or tradesman will know how to do hat, without glueing or messing up the brick wall. It's quick, cheap and secure, and best of all can be removed without much effort to allow you flexibility in time.

I think it really depends on the style and look that you want to achieve in your house - you should never give someone the advice to use wallpaper without knowing their design aesthetic. With that being said, I think that wallpaper is a lovely touch in older heritage listed home, because you can add the modern touch through it to the home, depending on the pattern.

Japanese!! Yes; now you've said that I can't believe that hadn't dawned on me before, but it's probably why I chose it in the first place. I do have a love of Japanese styling and there's quite a bit of it in other rooms of the house. The bedhead is a neutral linen so I think I could get away with some subtle Japanese styling around it. I like the idea of paper lampshades and Japanese style side tables. Thank you.

I agree paint may be more versatile - but the right wallpaper on a feature wall with that deer head would be so freaking awesome ! Depending on your colour scheme, if you go with a vintage or art deco pattern, fairly subtle and with a slight texture in it, that'll beautifully offset the deer. And if it's the right choice then you won't want to change it for the next few years anyway. So definitely wallpaper - there's some great 'wall candy' around :-) Good Luck !