I like the FRP suggestion.
The Pros are: they come in 4x8 panels, you can get them at HD, it is a quick and easy install, and, if installed correctly, are fairly waterproof.
The Cons are: FRP is spendy, the last time I bought it I think it was around $30 a sheet. You would need to install the panels over drywall, green board preferred, which adds to the expense. Installing FRP on a ceiling might be difficult.
"Thirteen" suggestion to use tile would make a really nice looking room. He is correct that you would need to use concrete board or hardi-backer on the studs to install the tile on. Tile is surprisingly easy to install. I would be more work than the FRP but the results would be really nice. You could use it on the ceiling but I would not.
Whatever you use for the walls - use cove-base molding on the bottom of the walls. Good luck!