If you want to remove ceramic tiles from a shower wall, then you will have to be very careful. Watch out for damaged tiles, and make sure that none break occur while you are removing them. Taking them down is difficult, and you should be able to complete it reasonably easily.
Step 1 - Warm Up the Grout
Heat the grout as much as possible. Doing so will make it easier to remove the tiles from the sides of your shower. Use a sharp craft knife to scrape the grout as it softens. The tiles will exposed for the hammer to strike.
Step 2 - Tap Off the Tiles
Using your hammer, tap the ceramic tiles from your shower wall. The tiles should be tapped gently to ensure that you don't break them, but hard enough to dislodged them. Put your putty knife under each tile and pry upwards. Continue to until you have pried off all of the ceramic tiles that you wish to remove.