If you use the same tile in the shower and on the floor it will be boring, not busy.

I believe you can. It will look uniform. Break it up, don't just set every wall in tile. Keep some of it in paint and use the white or off white. I would go with the wood porcelain look for this, it will feel more current.

You may not be this modern but the point I am making if the use of the porcelain. Change direction on the wall, The windows here, break up the tile, as does the vanity and walls in white. Keep it open and airy. If the bath is small, do not over use the porcelain. Think less is more, simplistic planes of color.

Just keep in mind about your floor tile for drainage purposes , but one thing I do see is your insulation should not be folded like that, cut it so it fits properly without stuffing it in too tight it should be fluffy as that is a big heat loss area if it remains unfixed and there is a gap in the right lower corner , bit off subject but easy to miss important items like this