I would stick with 12x12" tiles. Our foyer is about the same size (6x10') without a closet and I wouldn't want to go any larger than that. But then again, 12x24" could work depending on how your dimensions are. More of a square or long and narrow.

It's essentially a square, not a huge area. Do people make grout lines smaller now a days?

Yes, they do typically make grout lines smaller now. I like bigger tiles even in small places.

I'd pick the tile first and make the size/shape secondary as not all tile comes in all sizes. And yes, narrow grout lines is the style these days.

You can use large format tile in a small space. I used 18" x 18" in a small kitchen and a guest bath. The fewer grout lines the better. Your tile installer can help you select the right size and pattern for your space. We discussed this with our installer when he came by for the estimate.

Agree with the idea that the less grout, the better.

Bigger tiles, grout closest match to tile color, smallest lines possible....will look more streamlined and less busy.