I wouldn't use the same tiles, since everything might look bit boring plus it would create one great tile mass.

I would use one design for floors, one for shower and the other one for floors. You might even consider using patchwork in the shower

Here is a link that might be useful: Cement tiles - patchwork

I would probably carry over the tile from your shower. You already have 3 different tiles in your shower. You don't need a different tile on the floors.

I would use the lighter colored square tile on the floor and lay it on the diagonal. It will make the floor space look bigger and it will echo the diagonal one in the shower/tub area. If that diagonal tile on the wall is a larger square than the others, I would use that larger size on the floor too.

We are very happy with our Marmoleum floors in the baths and laundry. It is worth a look. Easy to clean, looks good and feels good to walk on.

I agree with badgergal, that you should use the lighter tile from the shower on the bathroom floor. Whether you lay it on the diagonal or not is not as important to me as the light color, and not introducing yet another tile.

Another vote for using the tile from the shower (the light ones).

As far as the paint color, it is really hard to tell on my computer, but it looks like the paint on the lower wall has more green undertone, whereas the tile has a more pink undertone, but that just might be the lighting in your picture.

I also agree with badgergal. I hadn't considered laying it on the diagonal, but it would add interest without another color or pattern.

Personally, I would change the bottom wall color, but wait until after the new floor is in. In any event, it seems to have too much yellow or something going on. It is at odds with the dark tile in the shower.