We've never had wallpaper in the kitchen, but judging from all of the instances of it popping up around the web, it seems like quite the thing to consider. It's colorful and playful, packing a strong visual punch:
Whether it's a somewhat traditional stripe (image 5) or in a non-traditional place (like up on the ceiling in image 10), wallpaper is one more material to consider when thinking of kitchen wall materials. Look for something scrub-able (at least as much as a good, durable paint) and let your imagination take over.
Do you have or have you ever had wallpaper in the kitchen? How did it work out for you?
Related: Glow In The Dark Kitchen Wallpaper