Yes, pinwheel or hopscotch... looks larger than 10" more like 12 and 2

It's Hopscotch, laid on the diagonal.

Thank you so much, Lyn and Palimpsest!

That flooring pattern strikes me as very 90s or early 2000’s. Is it just me who has that association? It is a nice layout for a mostly solid look with just a hint of detail. Why is it not used more often in transitional bathrooms we see on here all of the time?

Why is it not used more often in transitional bathrooms we see on here all of the time?

Mostly because the bathrooms we see on here all the time are copies of other bathrooms we see in here all the time.

Pinwheel is not very Colonial or very ”black and white”, even if done in black and white. That's mostly seen in travertine floors of the modern age. Not vintage.

There's not really an accurate bathroom floor for an 18th c. house because they didn't have bathrooms.

I don't know what you are considering, but if you want black and white checkerboard, maybe, this was done in the 18th and 19th c., sometimes.

This is c. 1800, so Federal, not Colonial.

The older name for hopscotch pattern is Pythagorean pattern, and it shows up in this Dutch Golden Age painting from 1665. The sizes are more similar, but it's the same layout. That's the interesting thing, it lays out the same with many variations between tile sizes.

Octagon and dot is another old pattern, this particular floor is French:

Instead of multiple colors on the floor, how about different shapes to add interest? Look for a quality porcelain marble look alike and use different sizes of the same tile throughout? That creates a cohesive look that isn't boring.

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I do like octagon and dot very much. I like checkerboard/harlequin as well, and am still considering it, especially since my house is actually more Federal than Colonial (a distinction I didn't make in my original post since not everyone is familiar with the difference and, as palimpsest points out, original 18th/early 19th century houses didn't have actual bathrooms). To me, though, it leans a bit grand/formal, and more suited to an entryway than a bathroom. I'm still gathering ideas and inspiration pictures, and I've considered gray slate-look porcelain tile too, but the main reason hopscotch appeals to me is that it adds some contrast without looking too dark or too busy.

The master bath is a room no one ever sees except my husband and me, so while we'd prefer something traditional, it doesn't have to be 100% period accurate--plus, again, the bathroom as we know it is more of a Victorian invention anyway. I like black and white because it feels more timeless than many other designs, and it's easy to find other bathroom fixtures that go with it.

Epoxy or urethane grout by an experienced tiler will be my choice. This site reviews grouts. Link.

I love a classic black and white bath - I feel like they age very well

I like your ideas and love black and white tile.

This is another nice look: