We are installing 2" Hexagonal Carrara Marble Honed tiles in Christian's main bathroom and Basketweave Carrara Marble Honed tiles in his master bath. Both will have a medium gray grout around them, which will bring out the various shades of gray while being easier to keep clean on both floors. The tile came from "Marble Online"; 60% off list price (about $9 and $11/sq. ft.) with free shipping.
Below are inspirational pictures via Pinterest.
We will also use white subway tiles and gray grout on some walls. These will be "Bright Snow White Subway Tiles" from Home Depot for $1.76 sq. ft.