I love those long floorboards/wood-look tiles and they are the feature so you wouldn't want something too busy on the walls... personally I would go with a larger format say 300x600 rectified edge white tile with a matt finish for the Hamptons look... what's your vanity?... a timber one would tie in nicely with the floors and all the white... very Hamptons :)

We're building 4x3.5 Two with ensuite and the others with a jack and Jill. Life has changed unfortunately and now everyone in the household works, kids stay at home longer and ageing parents sometimes move in for care. At the moment we have a 3 x 1 and really the only thing we really want for is a second toilet, which growing up we had because we had the one out the back with the red backs.

A floor to ceiling cupboard would work well in this space. As mentioned in the above comment using Mirror on such a large surface in the bathroom could become a hassle to constantly keep clean. However if you do like to look of Mirror I do suggest a dark tinted mirror, as this would go quite nicely with the colour of your tiles and not look to harsh in the bathroom. For the doors a Pocket door system would work quite well! this is where the door is opened and then you can slide it back to be in line with the cabinetry. I would keep the colours of this cabinetry quite plain and stick to the same colour palette of the tiles. Goodluck !

Thanks for the measurements, there were a few missing that would have made it easier to be more precise, But I'am making suggestions on what I think might fit within the existing floor plan which you are trying to do. the only small extension is to fit the laundry into a shared family bathroom. As there is already a shower and toilet in the current laundry I think it would be wrong to move them as they are close to your new alfresco area for the family to have easy access when you have your get togethers. To try and keep the girls bedrooms a good size and together with the other two bedrooms I suggest working with the fireplace and making the current Bathroom and ensuite but with the ability to share the toilet with the girls during the night. I have added my beloved barn doors to close off the kitchen from the bedrooms and also to be able to leave open during the day for extra light., the planned deck with roof over will make the dining/study/kitchen darker so you might need to consider a sky light. Anyway just a few different ideas trying to work with and around special features cheers