Labyrinth Wallpaper from 5.5 Designers
French design company 5.5 Designers have a quirky range of products and a slightly confusing website, but it is worth investigating for this inspired wallpaper.
The design is basically a big maze allowing whoever has a pen to make a path through the pattern, thus creating a design. It would work really well in a hallway where the pattern could slowly evolve over time. There is an additional design which is a massive word search - the words appeared to be in French which could improve your language skills I suppose.
The wallpaper costs 20 Euros from 5.5 Designers.