https://society6.com/ has some really cool shower curtains

May be yellow (mustard shade)

Двухкомнатная квартира для молодой пары · More Info

I think a soft green, like Behr Mountain Haze would be pretty. I also love SW Sea Salt mentioned above by Irene. In your picture, it looks like your vanity light and your mirror are brushed nickel, while the faucet is chrome? I do like mixing metals, but those are not two finishes I would mix. Maybe consider switching your faucet to Brushed Nickel? Or, if you do paint the walls a lighter blue or green--switching your knobs, faucet, and light fixture to ORB finish would tie into the dark tiles in your floor.

Agree with above suggestions for soft gray blues or greens with white towels & a white textured ( like a waffle weave or ? ) shower curtain. Are your cabinets as white as the floor tile? It looks “off” on my monitor. I’d play up the black & white .... either paint or replace the mirror with a black framed one, black & white framed photo art or drawings on the walls if there is space somewhere or over the toilet area.

Is that a bathroom for guests or kids?

I think with a lighter color it will make the room appear larger. Maybe update the shower curtain.