Consider changing the shower curtain to something more neutral that can compliment with the floor. Looks nice and clean in there, which draws appeal. Also, remove rug, will look more spacious.

White walls are fine. My advice: clean the floors super well and consider lightening the grout with a grout pen. Tedious work but would brighten the floor. Test it behind the toilet. Stark white grout wouldn't look good either. A white fabric curtain hemmed to the right length. A simple framed canvas picture hung with Command hooks over the toilet. Think abstracts, landscapes. Soft blues or greens paired with white are classic spa combos that read "clean" so my vote is white towels (but bath towels aren't out for showings, are they?). For showings: please close the toilet lid. Remove everything off the toilet top. Style the vanity with a luxe soap dispenser and a plant or flower.

Depending on budget, vanity hardware might be worth switching (can't see current well). If the realtor can't advise on home staging, consider hiring a home staging company. These types of decor investments are all market-dependant. Currently, many housing markets in my area have bidding wars and home staging is practically superfluous. Good luck!

If the tile grout needs cleaning I’ve found that mixing a paste of white vinegar & baking soda, applied with a toothbrush or a stiff grout brush works wonders. Ditto the comment regarding replacing shower curtain. Keep things simple & uncluttered.