Flooring Tile - Shower Tile Choices

I'm redoing my bathroom and I would like to know what are the best choices for the tile to use for the shower walls. I've looked at marble, porcelain and travertine and don't really want to go with ceramic, I want to stay with a natural stone. My challenge is that I don't want a wide grout joint to hold stains etc. I want a more solid look but don't want a solid panel. The shower is a custom built corner about 5'x6' with a corner glass door. I want a tile that is easy to keep clean, I guess that would mean non-porous. Any sealers that would help with cleanup if it is a porous tile?

Any suggestions would be helpful.

Thanks

Any stone in a shower will be high maintenance and need resealing over time, Porcelain would be the best choice and it looks just like stone.:)

I wouldn't use marble, granite yes.:)

Thanks for the advice. Does marble need to be sealed? How small can I have the grout joints?

Yes.:)

1/16".:)

how about good ol' glazed ceramic tiles? would those be ok on the shower walls too?