We used two of the lights - one over each sink. We did another bathroom in that house (we've since moved) - that bathroom was 5'x8', and we used one of the Artemide lights. It was plenty bright enough in there! We had the lights on a dimmer, which was really nice. Yes, our contractor built out a soffit above the medicine cabinets. It wasn't my first choice for how to do it, but it ended up looking really good. I wanted to recess the cabinets, but the Ikea ones are not made to do that, and the finish details were too complicated to make it work. So we decided on the soffit, which was much simpler. I wouldn't hesitate to do it the same way again.

Sativa has a good idea for a high contrast design but I might be overwhelmed too much dark black. It would need the balance of lighter floors and the natural light from the windows which could make it stunning. I bought the same pebble tile at our local H H Restore to re do our tiny shower. I want bright white tile like your subway tile but hubby still wants a large format porcelain. The mix from the pebbles can work with many things. Remember when it is sealed the colors will deepen to what it looks like wet. You could use a midtone like the charcoal grout for your floor tile if you are keeping the walls lighter like a warm white, tape or grey from the pebbles. If you go with dramatic black walls, you need a lighter grey ,taupe or warm white for balance. With either color scheme choose a basic floor tile with a bit of texture to prevent falls. A rectified porcelain with touches both cool grey and warm whites and taupes would work with lots color schemes. Keep in mind you may change your style in a few years. So pick a classic with lots of options. It will be easier to change a dramatic paint color than a busy tile pattern.

I would not do a gray tone... lightest shade of the existing tile color for a unified look with the texture of the tile. simplify all the add backs. blind, no curtain.

I’m chuckling over Rho’s comment too. But, I don’t know how you’d make this bathroom have an industrial vibe. I think I’d have left the floor tiles white unless they’re too bad looking. That box on wall - the vent - I don’t think you can put any cover on it without impacting its ability to ventilate the bathroom. Leave it as is. Is there a wall available to hang art? If yes, then use that space to create your industrial vibe - metal framed art. For textiles, I’d stick with either shower curtain color or porcelain fixture color. Or, go silver for a metallic look?