Answers

a stainless steel film will be easy to keep clean and won't do much damge to the wall when removed. http://www.amazon.com/Instant-Appliance-Stick-Stainless-Steel/dp/B00BAUPS9M

Tin panels for walls would look nice and can be cut to size and nailed on so it will make for an inexpensive and removable application to spice up the kitchen backsplash. Even adding color with paint by doing a pattern or faux finish can be nice to spruce it up and add interest. Just make sure you use semi-gloss for easy cleaning in the kitchen. You can repaint it to standard white before you move out.

Complemenary paint with countertops scribed to the wall is a clean look.  If you use eggeshell paint, it is durable too.