Hard to give suggestions without pictures

It would be helpful to us if you could post the picture of the room you saw on houzz so that we could see what you are seeing. But, without seeing the room, I agree that a white would be a good choice that will serve you well in the future if you decide to change the wallpaper. I would not paint the walls a gray because gray is fading in popularity. Any time you see a popular color such as gray EVERYWHERE, it's a warning that the color will be out of favor in a year or 2 or 3. I know that when I get together with other designers we all voice our tiredness with gray and are reluctant to specify expensive merchandise in gray. If you want a little gray in the room, use a couple of pillows which will not be very expensive to replace later on.