The white tiles seem pretty innocuous - what’s the reason for demoing them, redoing waterproofing and re-tiling with something white & simple?

A good tile installer shouldn't have any pattern mismatch when going from one section to another. Hire the right person!

There will be no mismatch if the tiler has any experience at all I do wonder why you are doing new tile ? No mosaic tile how do you think that would be better. IMO Ilke what you have so explain a bit of the reason for new.

People!! Remember your Pythagorean theorem ? Of course the edge of the angled wall is going to be longer than the straight cut wall.

The true height of the tile will be on the slanted wall going up to the ceiling while the wall with the window will have the longer diagonal cut edges where the walls meet.

I would get a plain tile and it is what it is. If it bothers you, go solid surface of large format where you will have minimal tile lines.

Thank you all for your comments!

After I posted the photo I thought "Wait.. that looks fine.. why are doing this reno"? :-)

Reasons are..

The tub is very grimy and stained. I've tried washing hundreds of times with all sorts of products. No luck.

Tub won't drain properly.

The drain valve is broken.

The tile grout is moldy. No amount of cleaning has gotten rid of it.

Finally, there's no proper exhaust out of the bathroom. So, we're seeing mold spots here and there.

As for tiles.. the floor is basic, classic marble. So, I was hoping for a bit of fun with the shower wall tiles.

We considered not tiling the ceiling and sloped wall. But thought that it might look weird and, perhaps, open us up to more mold/water damage in the future.