Ok, well if it is already a dark little room, are you sure you want to put that dark wallpaper in there? I'd be worried it will feel like a cave. Maybe you need to consider upgrading your lighting in that room. Of the vanity choices you show, my first choice would be the first one. Looks like Dark Oak and a Craftsman type style. That reads the most "farmhouse" to me...the other two are much more modern and the middle one reads very mid century modern to me. The little I've seen of the decor in the washroom doesn't make me think MCM would match. Would it be a LOT of work to get rid of the wallpaper? I think if you are going with the darker coloured vanity and light floors, I'd find a paint colour that works with the flooring colour a bit more than the blue does. Maybe something like BM Seapearl (below). Or maybe you put the colour below the trim piece and white walls above if you are going to have white toilet and sink. I do like the artwork you've got on the walls - very farm like and lovely. A very nice touch.

It can. You need good quality paper rated for a bathroom and very good ventilation (exhaust fan) that is used religiously! Better yet, put the fan on a humidistat and a timer.

palimsest I am for sure not going to do wainscoting. I really like where you showed what that would look like with the side wall papered and the fixture wall painted. The side walls wouldn't be too hard to do and I really do think it would look good. If I do the side walls in the paper and paint the fixture wall black then What is your opinion on my oil rubbed bronze towel bar, light sconces and tp holder? leave them, paint them(what color?) or replace them(what color?)

My husband is an old school paperhanger/painter (We have Gracie wallpaper panels in our living room - google it - is is worth seeing) and he will tell you peel and stick is ridiculous. It may be because he considers himself a craftsman but he dislikes it and won't hang it.