Polish and paint with silicate? Available in several colors if you happen to not like white. If it's well plastered and painted properly, I think it looks nice. Otherwise, you could install tiles? Nowadays, there are even tiles that look like wood, perhaps wainscoting with those? Or why not decorative stone? Granite? Slate? Extend the floor up the wall inception-style! More extreme might be going back to the 70s and building red brick walls or putting up a cool panoramic mural of, for example, the Garden of Eden or the Visby Ring Wall?

Jokes aside. There are ways to vary beyond designer wallpaper (but still moisture resistant) if you just think outside the box.