I like the green wall you have now. What is leading you to want to change it? Was it not your color choice? If you don't like the color, just repaint it. Wallpaper can be nice of course, but paint is so much easier. It's my understanding that grasscloth is challenging to hang correctly and is not for DIY novices. Beverly is also right, the room is very busy stylistically. You might actually be better off painting all four walls the same color to provide a more neutral background for your other elements. New nightstands and lamps would be a good place to start with a refresh if you're attached to your bedding and art. The lamps aren't bad, they just don't fit here.

May be paint accent wall ?

or entire room

And yes, I agree, definitely a mash up of so many different eras and inspirations...

Now English cottage style is trendy. Here is cozy bedroom with wallpaper.

It doesn't really look like you need to accent the wall behind the bed with wallpaper, however if you really want to, you might look at some wallpaper ideas before committing to doing the space. Below are a few bedrooms we have designed for clients that we thought also might help you.

Modern Farmhouse Rebuild · More Info

Modern Farmhouse Rebuild · More Info