Second one, which may be contrary to your local codes are those cheap
plastic panels some folks use to line showers.

There are two types of plastic wall panels. Both are code rated, they have a
fire-retardant. One is a white gel-coated fiberglass panel frequently seen on
the interiors of wall-in coolers. Their great advantage is that it is easy to
wipe mold and mildew off of them. Comes only in refrigerator white. 4x8

The second are PVC textured sheets. You see this in hospitals and commercial
buildings. Comes in dozens of colors. 4x8

Now comes the kicker. To meet firecode, both are to be installed over
sheetrock.

Dan