Lay them both landscape.

I am just wondering whether it is a good thing or not to go with solid colours like the dark blue (prussian blue), grey floors and white on other walls all in tiles. I see that a lot of designers seem to do a pattern on one wall, but I haven't found one suitable and whatever I do, I just don't want it to look out of date in 5 years time. I am not sure how about much of the prussian blue tile is appropriate in order for it to be noticeable but not too overpowering.

I like your 2nd option best. Will give your bathroom some interest without being too overpowering. Best of luck with whatever you decide.

I'd agree with most of Kates points , but some observations -- The existing floor tiles look okay in colour etc , but why is the height all over the place ? Is it worth reusing them and matching new ones ? That would be the size and colour I'd go for anyway . That 1950's green I personally don't think is a strong enough colour to make much of an impact on a feature wall -- I'd try and get about every 4th to 6th one in a darker Emerald green and get the tilers to add them in a random fashion . The mint isn't all that far removed from the white , and I'm worried it would not be as noticeable . Having said that , an Emerald grout ( I have no idea if thats an option , but it would be something I'd consider ) would add to the feature , and may be safer than a random mild and darker green mix . The rest of your design seems pleasant enough and willlook good -- I'd just up the effect a notch on the feature wall .