You answered your own question with your first sentence. Of course, it's okay. You'll have an intentional little sparkle. I like it already.

changing out the light and faucet is a start, but really, it's not much diff than what's already there you could easily get new hardware. maybe a matte black, or combined black and nickel If you want to modernize, how do you feel about doing a new floor? Painting the vanity? getting a new mirror? That tall, unframed one is just basic. I'd do a diff mirror, hang your new light, and paint your walls. doing a wainscot around the room is one way to bring in some interest. art over the toilet, new mirror Then I'd bring in some shelving or art (or both) over the toilet for some visual interest. do you have an idea of the type of look you want? what you have is nice, but it's builder basic. Doing some wallpaper is a start, but those floors are a little on the country side, so bringing in a modern type of paper may not jive well. you could always paint the vanity white, go w/black hardware, mirrors, and black ceiling (yours is tall so it would look fine). maybe do the shiplap or some other wall treatment.

Hmm. Well, I am usually somewhat in favor of not worrying about mixing metals. But I am not sure in this case what you suggest is advisable, nor that it will fix your "contrast" concerns. I would consider something other than gray on the walls to avoid a completely gray and white color scheme, and would leave the fixtures as you have them.

Your “linked” mirror would work nicely. You will never match metals unless you buy from one manufacturer so that’s unlikely. These golds are challenging to work with but they look great!!