Definitely paint the walls. It's a strong color and for many homebuyers, that's not a good thing. Here's an article on some grays that would work with your cabinet and the lovely flooring. You may want to pick a shower curtain (are you removing the glass doors? I'm not sure I'd do that and if you aren't why do you need a shower curtain?) first and then pick the wall color that ties the curtain and floor together.

Are you changing out the faucet? If so, what metal did you select? You can pick any mirror just about but I'd go with something with a slim frame that coordinates with the other metals in the room. Need to coordinate lighting with all the metals too.

Thank you! Great advice. There are no windows in the space so not sure how to pick a grey paint color for the walls. Should it be lighter than the vanity or darker? The hardware will be gold.

I'm no decorator but for my eye with the dark floor, the wall should be light. I'm going to tag @Beth H. : who is a great color expert and has a lot of good suggestions for gray walls and also has a good eye for lighting. Hope she sees this.

You also could add Design Dilemma to your posting topics and you'll likely get more people who are good with color.

Thanks so much!