A shower pan is sloped to a drain, and, as a result, the curves needed for the slope would cause large tiles to crack unless there are "relief" cuts in the large tile. You might notice these in public restrooms, but for a shower stall, the small tiles are more aesthetically appealing, plus, they provide more anti-slip surface than large tiles would due to the additional grout lines.

With regard to wall color, look at Benjamin moore color gallery. There is a Rhine River that is nice and any of the colors around it or in the grey green category below would be very restful.

I'm sorry I didn't have the photos uploaded. They are posted now. Thank you.

Grout is NOT tough to keep clean. Jeez, my grout's been in place for 17 years and never gets more that an after-shower spray cleaner once a week or so and a sponge cleaning every few months. It's as white now as when it was new. You must follow the tile manufacturer's recommendations.