Lovely sense of style! Bravo! We investigated porcelain marble look-alike tile but we decided on real marble which we will have to care for without any acidic products. Beware that there is a repeating pattern in marble look-alike porcelain tile like (on wall paper which will give away the secret.) We found great deals on Amazon and at Lowes for Bianco Carrara subways, pencils, chair rails and floor and shower floor hexes (1/3 the price of tile stores). We found a gorgeous remnant for our shower bench at a marble and stone shop at an amazing price. I can't wait until it's done to post photos! But back to your house... it's gorgeous!

Have you considered soapstone? I am putting that into my ski house bathrooms. It looks good with the wood and is dead simple to maintain. Engineered products with a honed finish have been problematic for some.

I like the wallpaper and the black/white floor tiles. It has a lot of pattern but I think it's fine for a guest bath. I would tile the shower area with green instead of blue, to match your vanity. Emerald green with black and white can look great. The paint your mirror frame black or green.

Here is a photo of the layout.