It's obvious that shower walls are the largest surface in a bathroom, so it's no wonder that the style of tile that you choose is important. Materials used in a shower must be able to stand up to humidity, clean up easily, and wear well. Shower tile options are natural stone (granite, travertine, marble, slate, limestone, etc.), ceramic, porcelain, and glass tile.
Natural Stone: The biggest drawback to natural stone is that it is porous. It will transmit moisture via capillary action. Special steps need to be taken in order to provide a quality, long lasting tile job. Travertine is very popular in the shower and bathroom floor. It is a hard and durable stone. If properly cleaned, Travertine will last a lifetime. Limestone is also a great choice. It is very durable and some limestone displays fossils. It requires a yearly seal, but the beauty is worth the maintenance.
Ceramic:Historically the most widely used tile. The draw back with ceramic is that the colored glaze wares in high traffic areas and is susceptible to chipping.
Porcelain:This tile is hard and very durable. New print patterns can be found to match any decor. Large 1x2 have recently become available. This material can be set to look like works of art by the right designer and mason.
Glass Tile: This is a very popular tile that has no place in a high moisture environment like a shower. Large tiles tend to crack (even when laid over an anti-fraction membrane). Moisture will many times get behind the tile backing and become visible. This is a potential nightmare. Small mosaics that have some sandblasted glass tiles may be okay but stay away from 4x4 or bigger.
The biggest mistake people make is putting VERY SLIPPERY tile on the bathroom floor. A glazed ceramic tile is a common mistake. A marble or granite...well, that's a neck breaker. The shower floor should be small mosaic 3' square or smaller.
Yes, I know what you're thinking... "won't putting a lot of grout lines on the shower floor make it moldy?" You need grout lines to give you traction. A good Panasonic fan will help dry the bathroom quickly. Leave the vent fan on for 15 minutes after showering to dry the place out. Make sure the contractor gives the shower a good slope to prevent puddles from forming on the shower floor. These things are critical to building a good quality shower.