It is not common, but a good choice. I think it is as safe as a subway tile.

These are 3 inch tiles.

1917 Bungalow · More Info

Here is a large square tile used in a backsplash design.

Contemporary Kitchen · More Info

Here are more large square tile in an offset pattern.

Los Angeles - Master Bathroom · More Info

I would say do not do it unless it is for your own enjoyment. That size tile to many makes things appear dated.

I have a shower that has rarely been used which has the square white tile. I'm having a hard time deciding to

I’m not sure any tile changes will have that much of an influence in updating bathroom in general. If it me, I’d leave until/if you were doing a revonation. In the meantime, more could be gained by painting walls and vanity/adding hardware, a new mirror and lighting and a large mat to hide the tile, as I think it feels much more dated than the wall tile (square tiles are coming back).

Hopefully a pro will weigh in, but I don't think you can just remove sections of tile without impacting the waterproofing. Horizontal accent rows (especially with stone) is also a dated look from before/after pics here or on design blogs I follow.

You cannot pop out tiles in a shower you will do damage to the water proofing and then need to rip it all out anyway. I think either live with it or redo it . IMO the fewer grout lines in a bathroom the better I like 12 24 tile on both the bathroom floor and the shower walls. BTW the white does not really work with the floor so you open a can of worms IMO. Add some color with towels a new wall color and a new sink and counter for the vanity.

There are some decorative waterproof caulking strips available on Amazon that you could try but I suspect that the grout lines would soon cause it to look worse than before. While not in the tub area some friends purchased a house where decals had been placed on some of the tiles. I think you would need to really clean the tile with alcohol several times except it does not appear to have a window or exhaust fan so that is probably not a good thing to do.

This is part of a renovation. I'm replacing floor and vanity and removing shower doors. Appreciate the feedback.

What if I painted on new waterproofing? Will that be less effective because it's not a single membrane anymore?

First thing to do is open the vanity doors and look at the wall to see if the same tile are there. Some vanities have a backing others do not. This bathroom could be the one I have in my house with several reversals, side of room, stool and vanity reversed. I just looked and there are tile in back of mine but my vanity was screwed into the wall so there will be holes in the tile.

Depending on the size of the new vanity it may or may not cover the area if it is lacking tiles. Then you have a decision to make as to do you remove all of the tiles because it is unlikely you can find exact replacements.

If a flip just leave as is or if the vanity is in poor condition paint to cover problems.

I would leave the tub/shower tile as is. It is very neutral and shouldn't bother anyone. Adding a border will make it taste specific and depending on what that border is will date it at some point. I would focus on all the other areas and if you are removing the doors then use a shower curtain and keep it closed and you'll never really see the tiles except when using the tub. Which I don't think anybody really cares if there is something else to look at when washing your hair and soaping your body. Definitely not an area where I would be spending my money.