Id go with shower quartzite. Imo the tile surround is too busy for vanity backsplash. is the floor staying? btw, you are fortunate not to have chosen marble as it is very porous and stains quite easily. Experience talking here

Thanks for the replies! I don’t think we can pull up the marble installed on the shower threshold and replace it with a quartzite without damaging the shower.

And, yes, the floor for the bathroom is staying. It’s dusty in the photos since it’s still a work area. It’s a matte Cotto colored tile.

I’d do the whole alcove in mirror and float the sconces through it, it will reflect back all the other pretty surfaces

You already have 4 different tile patterns/colors and 2 slab patterns/colors. I wouldn't add another one.

Have you considered continuing the short Taj Mahal backsplash around the back and then get fabulous mirrors and sconces. Sometimes less is definitely more!

The exposed bulbs in those sconces are hard on the eyes, specially that close up on a vanity.

well for the vanity wall, go with same material as vanity countertop

Matching the counter is a great choice. Second would be any of the designs/materials you already used. What shouldn't be considered is adding yet another material and design. The room is already a huge over the top WOW factor. You can't compete with it.

While all the options look beautiful, I think the first one using the same Taj Mahal quartzite is the best choice. As everyone says, you have a lot of different tiles/surfaces as it is, so adding another one is too distracting.

I love the arch and the mirrors!

You also aren't going to get the head on WOW factor as you walk into the bathroom, because of the toilet wall and glass shower enclosure blocking part of the views.

Make sure you select Starphire (low iron) glass for your shower walls to reduce the green tint of the standard shower glass.

Here are some photos of the details including how the marble looks against the Taj. If I can’t remove the marble on the threshold, I think I may use marble sconces like the ones below to tie it together. I won’t use these sconces if I take Taj all the way up the wall.

I also included the detail of the pattern tile on the fireplace and how it looks as a backsplash and also how the star and cross motif mirrors it (though the green color might be much).

Just following along. I like your choices so far!

IMO keep the backsplash to match the counters use the lighting and mirrors to add pizzazz

I think I’m going to go with the consensus and create a backsplash