First, I'm not digging the sliver cut tiles here. why not get a solid piece like the top and place it on the side as well?

**sidenote. make sure the tile guy uses caulk, not grout, in the joints between wall/floor, and all of the vertical corner joints. No Grout in these spots. I see you're using black (or charcoal) but I'd choose a white caulking for the floor/wall joints. 100% silicone caulk. mkay?

With this one I did a solid charcoal quartz backsplash (they come in 6") cut it to fit the curb, and then used the larger floor tile for the other side.

in your case I'd use the same white quartz since you don't have large enough white tiles.

You see on this one where they used the white quartz on the curb?

down the sides too, and the bench. you can also use it in the niche

On my own bathroom shower I used the marble floor tiles on the side, continuing w/the herringbone design, and a solid piece of carrara on top. here's a shot before it was completed:

(you could get a solid white piece of quartz and cut it to fit your curb top and down the side. They super cheap.get the 6" backsplash piece that comes in a 6' length. Or, you could get some of the same white wall tiles, but get them in a larger size. use those for the sides of the curb)

2nd, for the tile options, there are so many.

if you like the blue, what about the blue and white option?

the larger one in the right top, is a larger hex w/the blue star flowers.

Here's a light blue one shown w/a larger pattern tile. always bring in some type of wood for a bit of warmth

Or, go w/the multi color penny round, shown here in shades of grays

https://www.wayfair.com/WS-Tiles®--Value-Series-1“-x-1-Porcelain-Honeycomb-Mosaic-Wall-and-Floor-Tile-KL1005F3-L2970-K~WSTI1200.html

Silver Sage? I love the Bedrosians tile

https://www.wayfair.com/home-improvement/pdp/bedrosians-penny-porcelain-mosaic-tile-gsmt1557.html?piid=70866291

The Lagoon color is nice

https://www.wayfair.com/home-improvement/pdp/bedrosians-penny-round-mosaic-1-x-1-porcelain-penny-round-mosaic-wall-floor-tile-gsmt1553.html?piid=36930279

white oak vanity would look nice w/any of those blues or greens,

Bedrosians also has something like this

You could do something like this w/the black and white, (or even do the blue and take out the spots for white)

The Marin (bedrosians) version is a good price and has the 2" rounds in this misty blue

https://www.wayfair.com/home-improvement/pdp/bedrosians-marin-2-x-2-penny-round-matte-porcelain-mosaic-tile-bedr5168.html?piid=98041089

Hudson tile has a 1" or a 2" (I think the one blue option you show is the Marine color of this Hudson tile)

this one is Frost Blue

diff colors

https://www.wayfair.com/home-improvement/pdp/merola-tile-hudson-1-x-1-porcelain-honeycomb-mosaic-wall-floor-tile-w001942202.html?piid=1525303836

Or, what if you did the 2" star and cross option?

comes in white or black, matte or glossy

here's how a black and white would look. notice the white quartz curb top. on the side it looks like they used the white subway tile. (would have looked nicer w/the quartz continued down the side. )

love the wood vanity option w/any of the blacks and whites.

Here's your white shower tile w/black penny round floor, carrara curb, and a black baseboard (this is outside the wet area, obvisouly) w/a geo pattern black floor tile.

Instead of that geo tile, I love this Aster black hex tile w/the white lines. I've used this in another bathroom design. (comes in blue if you prefer)

https://www.wayfair.com/Merola-Tile--Aster-9-x-10-Porcelain-Patterned-Wall-and-Floor-Tile-FCDASX-L2970-K~EML10880.html