Depending how vivid your scarlet is: You can go with white or cream so it really is the accent wall and nothing is shouting for equal attention You can also go for a muted grey or beige

Gallery walls are popular. You can do a nice geometric stencil in a metallic. But I'd prefer wallpaper. You can match your paint color to the background so it looks like a stencil, but it's faster and you'll have fewer imperfections. Many patterns come in temporary papers made for renters if you are worried about the removal process.

You can get a custom wall art done , glass with bronze, glass painting, that wall should be a center of attraction, anyone walks. I have done this for a site, it works wonders, guest appreciate a unique feature. this can be done as DIY project on weekend also. these are some some real world executed ideas. cheers mate.

I would suggest u to go with white sheer and light grey curtains only. If u want want to play with bright colours then it is safest if u add them in form of accessories or decors, reason one being the space is small n it’ll look more crowded then. It’s better if u avoid orange n yellow in this bedroom at least. If u can give a better picture of the accent wall colour here it would be better. Then u could go with a darker shade of it to form the colour scheme. White+Grey+Purplish brown. That’s it.