You haven't mentioned their ages, but I'm guessing you want something they can grow in to? something classic and timeless, but with some personality?
Here's a basic rendition of your size bathroom. ignore actual tiles used, just loo at the overall layout/design. do you like the tile wainscot around the room? (I always take tile up to the ceiling in the shower area)
I have a ton more pics for you to peruse!
Anyway to take up this soffit? or is that just an upper cab? in any case, I'd remove all of it
You'll also want to bring in ample lighting. Do a center ceiling light (with 3500 K bulbs) as well as a vanity light or sconces. Replace your air vent w/something better.
I came across these larger format porcelain tiles that look like terrazzo. They've at HD listed under Emser tile/ Terazio. they have diff sizes. it's a matte fininsh.
you could do these on the wall w/the decorative tiles on the sides, or just on the back wall
Or, use them on the floor outside, and for the shower/tub surround, try the bedrosians tile in a similar layout. this is a cross-hatch or basketweave pattern. (Are you keeping your tub?)
For your vanity, since it's small, consider doing the wallmount faucet like shown in this pic^. you will gain a bit more counter space AND it's easier to keep clean. Do a simple vanity like shown, quartz top w/the 4" backsplash surround.
If you were going w/the larger subway tiles, I'd do it like this. stacked layout (or some of the other designs if just doing one wall) I don't care for this particular niche, but you should have one on the side wall that has ample storage for bottles.
Here's a similar tile in the vertical 1/4 offset. it's a bit diff looking but has a nice waterfall effect. Again, use on back wall, side wall gets the larger tiles. (if you prefer) also notice the fixed glass panel. in a smaller bathroom, this gives you a 'larger' feel.
I did my neighbors 5x8 bathroom. We went w/an inexpensive vanity and remnant quartz top. This was an offset sink (drawers on left) Obviously this picture wasn't complete!
Colors I used are shown in the photo. for the inset, I told her to do a few shelves (wood or glass is fine) and have it look something like this:
If you like this look, copy it! I love the wood frame mirror if using cooler-toned items.
Here are a few similar size bathrooms, before and after
The Bedrosian tiles I showed you can be laid in this manner on the back wall. for the side walls (not shown here) you can do the larger format white tile, if you like.
Notice the shelves behind the toilet. good for extra storage. get some baskets or jars for toiletry items.
you can do these yourself for less than $50. get a piece of wood, have it cut to size, sand, stain if you like, coat w/varnish. get a few brackets
I also like this idea.
If you like the more natural, boho look:
Try this w/the terrazzo looking tiles in the shower, and maybe these for the floor
Bedrosian, porceling 9x9 Vivace.
You could do the marin tiles in the shower as an accent on 1,2 or the 3rd wall.
this is the same size as your bathroom. Your ceilings prob aren't as tall, but everything else is the same size. you could totally do any of this.
Notice they did the black herringbone on the back wall, side walls are white. You could opt to do the white terrazzo, larger tile on the floor to make cleaning easier. Use gray grout inside and outside of the shower.
This is a white vanity w/either Super White or a porcelain or marble counterotp. I'd still wall mount the faucet for more space and easy clean. Don't know if you want to switch to glass doors or keep a shower curtain. The vertical T&G is a nice touch, I have another pic of that below.
Sticking w/the black and white theme (I'd use a natural oak vanity and white top and a textured boho shower curtain) you can lay out the shower surround tiles something like this:
Of course you could switch out the colors to anything you like.
You had asked about the Schluter jolly. I used them on many projects.
In my niche I used the gold one on the inset for the border around the marble
And on the outside border used the larger black one. they come in diff sizes, as you can see. The Jolly is the one you want.
Here's a mostly white bathroom with good lighting (don't forger a waterproof light in the shower) . You could choose a diff color vanity, or go w/a neutral vanity and tiles w/color
Don't forget the shelves.
I love this whole look. ignore the double vanity. you could easily do a single, with the wallmount faucet, tile backsplash as well as tile wainscot around the room.
If you take out the tub, the room will look a bit larger. but either way, this is similar to how those Marin tiles (or the Makoto tiles) would look. Taupe vanity, plank flooring
another option to get more bang for your buck, T&G paneling painted in a contrasting color
They used Blue here, but imagine those black and white options w/the white oak vanity.
I don't normally like the 12x24 tiles on a tub surround. to me they're too large.
But these larger hex tiles? I like how these turned out. this is a porcelain tile that looks like cement w/wood inlay. Tilebar has them. (or try IvyHill on wayfair)
As you can see, lots of diff ideas that you can use.
Q