It can either look really dramatic or too dark, depending on the size of the room as well as your other components. I've attached a couple of images of our work using dark tiles, the smaller bathroom we have surrounded the bath with dark tiles but then balance it with an extra large mirror to bounce the light around the room. The larger bathroom we have taken the floor colour way onto the wall but used a different texture on the walls for drama. Hopefully this gives you more of an idea but you shouldn't to nervous of the room being dark, it's where you can create a contrast as well as textures. Look forward to seeing what you go with in the end.

It could be horsehair plaster. Plaster used to be re-inforced with horsehair, but it looks more like fibreglass strands. Horsehair matched the period of the original home, whereas fibreglass doesn't. Best of luck, Dr Retro of Dr Retro House Calls

This is an ideal situation for a very short toilet. why do so many of them stick out from the wall SO far. Here it would be great if the loo was minimum eg. 450 from wall so as you can get past it easily. Yes you can use an in wall cistern but often the pan is still sticking out like a sore thumb. I would love to see a loo that is no further out than a vanity: neat, tidy discrete.

this is a much bigger changes than just a wall and involves foundations, floor and roof as well as plans and Council Development application but the plans imply that you will be making the building smaller which is a very unusual choice but you will need to ask a builder for quotes