High contrast is a modernizing tile strategy for bathrooms.
Grout is as permanent as cement. Neither the color nor the thickness can easily be changed. So choosing dark dark grout (i.e. not white) for white tile walls in a bathroom or kitchen takes careful consideration no matter what shape or size the field tile will be. The rap on dark grout is that it can appear dirty with white tile. Traditionally, white grout is the safer choice which unifies the look of the wall. But the practice of going with gray (or even brown) has became popular as a way to keep white bathroom walls from looking bland, institutional, or retro.
In a traditional bath [top], 6 x 6-inch white field tile was set in a staggered pattern . I must confess this is my favorite way to see square tile used on a wall. The pattern and richness is emphasized by gray grout which also helps tie the wall into the brightly patterned cement-tile floor.
Rectangular tiles, stacked in neat rows, was revived from mid-20th century style bathrooms but works well in contemporary baths with modern fixtures. Large-scale field tiles (these appear to be 3 x 12) can create an illusion of space and darkening the grout almost creates a paneled effect with these.
Any size white subways are classic when staggered (though I’ve actually seen them stacked in New York subways). These fat ones (which look like 4 x 10s) add a masculine air to this modern bath and escape that same-old-subway look thanks to their size in combination with beefy lines of dark-gray grout.