The first image looks very serene. Scrolling to the second image I audibly said ”Ooof”. It’s too much impact, maybe not what you want in a bathroom? I do like the varying tile shades in the last image, like shadows on a pond.

I would simplify by choosing one stone as the dominant feature and letting the other materials support it. If the Calacatta Viola slab is the focal point inside the tub arch, use a quieter, more consistent surface for the vanity and shower surround; repeating a strongly veined stone in several large areas can make the walnut and taupe tile compete instead of connect. Before ordering, place full-size samples together in the actual room in daylight and at night, because warm plaster, walnut, brass and taupe can shift the apparent undertone of the stone. For the arch, a slab will usually read calmer and make the curve feel more intentional than small decorative tile, but ask the fabricator for a dimensioned seam layout, edge treatment and vein-direction drawing first. Also confirm how the stone will be supported, waterproofed and sealed at the curved transitions. If the slab needs several awkward joints, a restrained tile with carefully planned grout lines may be the cleaner choice.

I LOVE marble = I love the drama of the stone slab over the tub. However, I would NOT use two different marbles in the same bathroom (actually, it looks like three different types in the renderings -(i) vanity countertop, (ii) floors + inside shower + on shower bench, and (iii) inside of the arch over tub).

Calacatta marble has veining - some types have very dramatic veining and other types have less dramatic veining - however, they all have visible veining. Some of the marble in your inspiration photo looks like a different type of marble than a type of Calacatta.

I would use a dramatic slab of Calacatta marble other than Calacatta Viola - while it's very popular right now, it is very limiting if you would want to change up the color a bit in your bathroom in the future. I like the marble shown as your vanity countertop - I would use the same for above the tub. I would use microcement around the the tub arch + inside the shower. Personally, I don't like shower benches - they are cold = not one sits on them + they tend to be a place where leaks occur. I'd rather have a foot rest for shaving or a teak stool.

I am not sure about the tub. While I like stone tubs - I'd probably go with a more neutral color.

However, if you love the Calacatta Viola marble - you should use it - however, I'd use it for the countertop also + bathroom floors (if you want to use marble on the floors). You need to make sure that the color of the tub works with the colors of the Viola marble veining.

Yes, the idea is the same marble throughout. These images were created in AI ChatGPT, I believe, so it somehow made the marble look different on the countertop and in the shower. I def. will do microcement or limewash around the arch.