I wanted a more cleanable backing behind the stove--after thinking about it all winter I decided to go with aluminum kitchen wall shield that's used beneath range hoods. It comes in 24x36 sheets with a different color on either side. I got white/almond but there's also white/black. I bought mine at Lowe's for about $20/sheet--it's hidden back with the stove parts. Because I had to cut one sheet shorter for the side next to the refrigerator I got a damaged piece for $10 and I was able to cut out the bad bit.
The almond side would have matched the interior better but I used the white because it was brighter and it was easier to match the paint for the trim piece and caulk. (Either my eyes are getting old or the interior of our 171 is pretty dim.)
I used silicon caulk around the back edges and a S-pattern about 2-in apart across the entire back and put the pieces in place. (Note: things aren't exactly square around the galley.) Every 6-in I drilled the edge (to match the pre-drilled corner holes) and used 8x3/4 chrome oval phillips automotive screws (also at Lowe's in the specialty screw drawers). They don't look too bad and I can always go back and paint them.
Next I rabbeted a 2x2 to accommodate the trim on the back left wall and then cut a 45 bevel on the front. I drilled and countersunk 4 holes in the center of the front face so that the holes came out on the back corner diagonally across the 2x2. Using more caulk I attached the trim to the back corner with 8x1-3/4 production screws. I then caulked around the bottom edges where they meet the counter.
It looks OK if you stand back 50-ft and squint and it's a lot brighter in the Pod. It's easy to clean with 409 and the suction cup soap racks seem to stick. Magnets would have been better but this aluminum was so much lighter and relatively inexpensive compared to the other options discussed here. The aluminum and silicon should also allow some flex.
Here are some photos--I should have taken a photo of the end of the trim piece to show shape.
For other ideas I originally started a topic to ask what other folks had done at:
http://www.rpod-owners.com/forum_posts.asp?TID=3014&KW=&PID=28486&title=kitchen-galley-wall-covering#