I forget the exact measurements of mine, but I decided against using the smaller tile, because to my eye, they looked too small. Don't know where you are located, but I found the larger ones at Nemo Tile Co. in New York City. They have them in stock, in white and a few other colors, and you can pick them right up. I will say, however, that the smaller ones might be more historically accurate. In this particular bathroom, we were trying to stay true to the original bath, which did have hex tile, in the smaller size, but they were too broken up and too many pieces were missing for us to salvage. We also had to open up the whole floor anyway, so we had to replace. In looking for replacement tile, I just thought the larger ones looked better. Sorry this isn't a better picture of the tiles themselves, but perhaps the other shots might help you to decide. Good luck. Here is a link that might be useful: My kids' bath

That's all a matter of preference. Not seeing the tile, I generally prefer diagonal. For some reason I prefer not to have all the lines in the same direction, so having the tile at an angle to the wall and cabinets just looks better to me. But some people don't like that at all. There's some good discussion on this in Bathrooms if you want to do a search and read while waiting. No feelings about grout lines other than I know I can't keep them clean, so I would go small. Not sure if these are regular tiles or vinyl, but for regular tiles make sure you ask about lippage. That's when the tiles are not even heights, less/no lippage is better, but harder to do. I don't know all the technical stuff, but good info on Bathrooms about this too. Maybe just bringing it up will encourage them to be on their toes?

We had a similar experience except we didn't come to terms with our dislike of the tile until after it was installed. After ripping out what was originally installed, and getting some great input from this forum, we went with NMVS 662 Rust from Noble. Below is a link to our build thread if you want to see pics. Scroll about half way down. We're now very happy with the final look. Here is a link that might be useful: Our Build Thread

I like the first picture over the second. I just installed 12"x12" natural black slate tile with a 6"x12" border in my kitchen. I put it on a diagonal. If I were using your size tile, I would do the running bond across the room rather than the length of the room. I also used a dark grout, charcoal rather than lighter grout. I had to use a transition strip because the proper underlayment raised the level of the tile enough to require a transition strip. You may have to do the same. It's not the end of the world. It protects the tile and wood floor and provides a visual cue that the level is changing. We don't even notice it anymore.