How about the same decorative tile on the wall behind the vanity? . I agree that a wall paper would compete. It is a lovely tile but I don’t think it was the best idea to put it on just that wall. A large piece of art could have worked there.

How about a simple grass cloth wallpaper in a neutral beige?

There are great vinyl grass cloths that would work great in humid bathrooms.

I would finish the bathroom and only then decide if you need wallpaper at all.

You might be getting carried away with the feeling that you have to fill every wall with something interesting ...

Wow that too many materials in such a small space. Now the best you can do is a texture.

Select some decent light fixtures for this room BEFORE you select wallpaper.

This is an example of when someone fines too many clever interesting tiles and tries to combine them in a small space. They lose effectiveness. That linear border around the floral tile just makes everything worse.

Im curious as to why tile had to be on that wall. it appears to be a tub area.