You might consider something like beadboard... inexpensive, could even be a diy project, and is easily painted if you want to change color. Painted in a higher sheen (satin or semi-gloss) it'd be pretty easy to wipe up. (FWIW I have just a painted backsplash (wall, not beadboard) in eggshell finish and it cleans up fine and has no stains after 7 years.) The color choices are as endless as paint choices- you could choose same color green as what you plan to put on wall or pull another color from the wallpaper you have selected.
Q