Tile is about the cheapest cladding material there is, other than the cheap acrylic walls sold at home centers. It can also be the most expensive if installed incorrectly. Installed correctly, by a Pro, with proper waterproofing, it will be an average cost choice. As in 5-7K for a shower. Cultured marble will be more expensive for the material, but the labor will be cheaper. They end up about the same average cost.

You need porcelain tile. Go to a tile store near you. There are "thousands" from which to select.

IMO cultured marble looks like plastic , which it is. Go porcelain tile , large format to cut down on grout lines and have a great looking shower . BTW this should have all been decided before starting the shower.

I would go to a local tile supplier. There you should be able to find a great looking porcelain or ceramic tile that will have a classic marble look or a natural stone look. Tiles can range in price so always beware of cost per square foot.

Depending on the size of your shower and the square footage you should be able to work with a budget of around 5k all in. That includes backer board, waterproofing, shower pan, tile installation and cost of tile. Then you need to think of inclosing the shower with a glass door or shower curtain depending on your budget.

I did ceramic tile that looks like marble