Place tile on the diagonal, that will widen the room and make sense of your larger floor tile choice.

Your concern is that they are too large for the space? You want more grout lines? What type of tile is it. Porcelain, limestone ... ?

That depends - is it the new kind of rectified tiles with perfectly smooth edges that can be set 1mm from one another, with basically invisible grouting?

Or is it regular, curved edge tiles? If it is the latter, I agree with you - find a similar, smaller tile.

If it is the first, the idea is to use massive tiles so that it looks like a solid floor surface - so go for it.

Marie-at 18 x 18 I can fit one full one on a diagonal and then two "triangles" on each side. tile is a travertine looking porcelain. Pic 1 is diagonal and pic 2 is lined up where tub will be. Pic 3 overall space (L shape after wall goes back up) entire space probably 5x10.

I suggest you have them cut them in two, into 9 x 18s, which will be a more comfortable fit for the room, while giving you the tile you like.