A dark grout might seem different, but so long as you don't look for a grout that is usually so dark this looks black, you ought to be fine.
Finally, having all the walls within your bathroom tiled not just makes for some other look, but the walls will be much easier to completely clean because you can certainly just run any sponge or mop with the tiles.
For tiles which might be not so sleek, you can possibly space the tiles firmly together or leave a smallish gap. A 1/8th-inch gap belongs to the standards used with tiling.
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