If you decide not to replace, you can cover with Tile covers, Plain, Patterned and Metallic.
Chisel out old broken Tile, old grout and old Chaulk. Vacuum all debris up. Wipe cleaned out area with rag. Mix or purchase already mixed grout for shower. Place enough grout in area where old tile was removed to hold new tile. Roughen up grout with grout tool or you can use a plastic knife blade to toughen area. Place new tile over new grout. If more than one piece, use a spacer for tile before placing another tile in grout. One at top of tile and one at bottom (or one at left corner and one at right corner) on the side where another tile will be placed. Let dry according to directions on grout you used. Then grout on top of tile and wipe off. Let dry again. Last, chaulk and let dry 24 hours before allowing water contact. Happy tiling!