You're always on my mind "banana leaf wallpaper" via Pinterest
As much as I love wallpaper, by far that's not the reason why I believe powder rooms look more inviting when wallpapered.  Of course big part of that inviting atmosphere comes down to the choice of paper, but the enveloping feel of a beautifully finished powder room does make a guest feel welcome more than any other room.  Bare powder rooms are boring, there is only a toilette and a sink and unless they are not covered in expensive stones and embellished crown molding or painted in a nice color, there is no visual interest at all. 
It's also the place where more design-conservative people can test their courage and opt for more bold design choices they would not pick for any other room in their homes.  Enjoy!
 A very cool and fresh powder room in blue.
 Katie Ridder.  De Gournay wallpaper
 Lorenzo Castillo?
Grrrr! by Linda Chase
 Timothy whealon
 Isabel Lopez Quesada
Dona Remember