Who says that wallpaper has to be as wide as it is? We have decorative (horizontal) wallpaper borders, so why not wallpaper itself?
Today’s invention is strips of (vertical) wallpaper which are much narrower than normal (eg perhaps 12 cm wide).
Although requiring more trips up the ladder, these would have the enormous advantage of being very much easier to paste and hang around tricky surface features (eg corners) than the usual stuff.
Once the first strip was hung correctly, using a plumbline, the others could be very easily butted up against each other. This would obviously work best for paper with a bold, vertical, striped pattern; hiding the joints and making pasting and pattern correspondence between adjacent strips very easy.