Other than the wall colour, what do the flooring and the vanity look like?

---------

Just read your question again and if it's only about the size of tiles, as below, I've also used 12 x 24 tiles and they work out very well.

I used 12x24 in a similar sized shower and feel it works well.

The flooring hasn’t been decided, but here’s the vanity.

Here is the vanity

Taking off the surround but do the walls have waterproofing? Sustrate suitable for waterproofing? How will you tie in the waterpoofing with the tub? These are not a simple one for one replacement typically................

I didn't think about this. So I will need to remove the gyproc and replace it with the sustrate? Will this be enough? Thanks for your help

Watch this before deciding if you want to replace the liner with tile. https://www.youtube.com/watch?v=vC6Il3vPt0E

The picture showing the lip of the tub is a little odd for a tub/shower combo. Can you show a picture of the tub....looking down at the rim?

The first four minutes alone of @Jennifer Hogan 's video are super informative.

Cement Board then Redguard (or a waterproof wall board system like Kerdi) before the tile but you will have a difficult time tying the waterproofing into that tub as that appears to not be a tub designed for a wall tile.

Once you work out the technicalities-get lots of tile samples that take into consideration your floor color. If you go with a solid bright white tile in the shower it will only make your floors feel drab and ‘off’. I like a medium scale square tile for your bath - and finding a bath mat that brings in some black would be nice. This one is from Crate and Barrel. Also, think about product storage in the shower and how that will work - corner wire baskets vs a niche vs a Kohler Choreograph Barre, etc. Lastly, how you edge the tiles and grout color. Discuss all details with your vetted tile contractor prior to ordering anything.

If you are replacing the floor you would start with that selection first. Since you have a black/white vanity you could consider a lot of different options. For smaller bathrooms I like a smaller scale floor tile - all of these look great with a simple white tile in the shower.

These are great ideas! Thank you.