To get a modern feel with that vanity, i think you'll have to do the rest of the space pretty stark/minimalist -- maybe a silky medium gray paint and a very plain, maybe industrial feeling, mirror. Not sure anything else about the room can stay the way it is -- the vanity will really be the star, and all the art and color choices will need to support that. It looks like your flooring might need replacement anyway. I don't have the time to find a really perfect inspiration pic, but here are a few that might point in a direction... Dunno if I'm conveying what I have in mind, but anyway, modern + elegant is quite a nice mix!

Subway is always a safe bet. I'd do a color matching your counter top, then dark gray-brown grout with a high-up accent line with a pattern of tile that brings in the gray-brown AND the color of your bathroom cabinets. Also....highly recommend framing your mirror with same arts and crafts look as your cabinet. You can purchase a long strip of wood, stain it to match and have a lovely tied-together look. See Prairie Window Grid designs on Pinterest.

These questions are mostly going to be opinion/preference as they are aesthetic in nature. Some of it depends on whether you're going for a traditional or modern look. Personally I don't like stacked subway tiles, so I would stagger. If you do go with white subway tile, small hexagonal floor tiles, white with some black, pair really well and are durable. As far as height goes, if you stay 4+ inches above the sink, it will double as a back splash.

Dear Weedyacres: One bedroom is 13 x 25, the other is 12 x 18. The other bathroom which is not in the drawing serves two bedrooms and one of those bedrooms is really tiny. On the other side of it is the dining room, so no way to make that smaller. I guess the only possibility at this point would be to loose the tiniest bedroom and turn the current master bath into one with the spiral shower, but I don't like that idea at all because we mostly heat that part of the house with the fireplace and I wouldn't want to loose a bedroom in the main section. Plus I think that really might affect resale value. Probably best to leave as is. I am so thankful for everyone's input because I think it's helping me to see that the spiral shower is a no go. Actually, the house isn't the main feature for me. The main feature is the two acres and lots of woods and the sun room with wall to ceiling windows. And the room we will use for dancing which actually brings me to another problem. The house is on a slab and we want hardwood. Sounds like engineered is the only way to go. We keep this room about 50 degrees and we want something that won't hurt our feet like tile would do. Thanks again for your help. I really do appreciate it very much.