If you don't have enough patience for the Rasterbator (DIY solution), then MyBiggerPicture.com offers an easy way to take your own photos and blow them up big enough to paper your whole wall.
MyBiggerPicture.com is devoted entirely to helping you put your photographs in places where it needn't necessarily be (but you might want to nonetheless). You send them the pic and they'll make it into wallpaper, ceramic tile, fabric, chairs, bags, bowls and even large canvases. Prices are not cheap and shipping will add cost, but since we don't know where else you can get the wallpaper, it will be worth it to some. (Via Mod Mom via Swiss Miss)