I am removing the tile and replacing water-damaged walls in a small shower in my master bath, and converting it into a linen/storage closet. How do I close off the drain? I'm assuming this is a must do to prevent the possibility of drain back up and/or odor, yes?
If it's a perminant removal I'd cut the pipe off as far down the line as you can without disturbing another drain line and using an appropriate cap for the type of drain material. Sweat for copper, glue on for PVC, quickcap or equivalent for cast or galvanized. If you may put the shower back it's a different story.