The 12x24 are fine in size, just stick to something with less variations given the space.

12 x 24 seems like a good size

My daughters hall bath is 76x51 so almost the exact size of yours. She used 24x24 on her floor and matching 12x24 on her tub/shower walls..

Here's an in progress picture

and completed

Be careful if doing it yourself and going big. I'm currently renting part of an old house and whoever tiled the floor here, didn't get it quite level. The floors sag and hog depending on temps and the tile is cracking. It's not as forgiving as wood or Pergo; so, the smaller you go the better your chances of keeping it crack-free.

i had our similar sized bathroom tiled in 24x24 tiles but put them on point ( ie look like diamonds as you enter room)- really made the room look bigger

Most important is Not to use white grout. With any of the sample tiles in your picture, use grout that is close in color to the tile. Not good to use a contrasting lighter color grout as in ArchitechturalDetails picture.

Hi agroark, first, I am wishing you a stress-free remodel! Next-- a large format tile in a small room absolutely looks great, but you should consider the style of the fixtures in the room and their placement, and the style you want to evoke overall. Are you re-doing the shower stall and changing out the toilet and sink? You should choose a tile that can easily flow into the shower. If you want to do a Victorian era cottage, you'd best go with a penny tile. If you want to go more in the way of a modern glam, a 12x24 is great. If you want to go with a relaxing Zen style, go with a large format tile.

If the door will remain open at all times except when in use, go with a faux wood-look tile 6"x36" to match the hallway. If you are not changing out the shower, and this is only a cosmetic update, I'd go with a floating wood-look vinyl tile 6"x36" or 48"--whichever size you can find, and run it front to back, from the door to the back wall. You can install it right over top of the tile floor, just make sure the floor is scrubbed clean and the existing grout is sealed. Then you can chip off the "baseboard" tile and replace it with real baseboard. You can also paint the sink cabinet in a soothing color that contrasts with the wood-look vinyl...a sage green would complement it nicely.

I think the size of the tile is fine. I like the lighter one in the top left close to the vanity.

We have 12x24 floor tiles in our standard 5’x7’ second bathroom. Since the bathroom‘s width is only the 5’ bathtub on the back wall, we had the tiles laid horizontally to try to widen the room’s feel.

Maybe it wasn’t correct to lay the tiles horizontally in a 5x7 bathroom; I really wouldn’t know, but I still like it against the hallway wood.

PS to the above, I couldn’t get a photo to attach. Anyway, our hallway wood runs the same direction as yours, opposite direction of our 12x24 :)

We tiled right over the vent in ours and that was okay with the inspector. The vents are huge in a small bathroom. We went with 8 inch octogon tiles alternating a pattern with solid.

I think this space would look great with either a larger format hex tile (there are some great ones that mimic terrazzo now) or a herringbone pattern. Both would give great interest to a smaller space (and surprisingly, elongate the room and not make it look smaller). Agree that the grout color should more closely match the tile, particularly if you are worried about keeping it clean. You'll have to play around with tile sizes to see how much pattern you can achieve in your space. Check out how the updated floor register looks on the hex floor in photo attached!