The decor drives the heavier travertine look. As above, and introduce some greenery like a nice plant in the corner of the bathtub area.

just changing out the fixtures to lighten up the space, as in weight/profile and color.

Like polished brass or champagne, even a rose gold tone.

Slim mirrors, soften the decor items, and edit.

I'd paint the vanity cabinet, but if you lighten the wall color, the wood tone is fine.

I'd look for a wall color that is similar to the tub color, an off white/ creamy white,

like SW Alabaster.

https://www.bedbathandbeyond.com/c/towels/washcloths?t=18655&featuredproduct=33905187&featuredoption=63632458&ci_sku=38275450-000-009&cnc=US&cid=323867&type=pla&targetid=&track=pspla&utm_source=google&utm_medium=pspla&gad_source=1&gad_campaignid=18575175996&gbraid=0AAAAAD_EGx8kC84rwPBX8yPQ7dhadRiQK&gclid=EAIaIQobChMImfvNu5jPkQMVTXR_AB2feidUEAQYAiABEgKf6_D_BwE

https://www.wayfair.com/Everly-Quinn--Denroy-3-Light-Dimmable-Rose-Gold-Vanity-Light-X117945873-L6116-K~W006834762.html?channel=GooglePLA&ireid=201230821&fdid=1817&refid=GX711703821248-W006834762&device=c&ptid=2435976069491&network=g&targetid=pla-2435976069491&gad_source=1&gad_campaignid=17748912450&gbraid=0AAAAAD9ISC6lhM-pEHOnY7b5y3KxwVK37&gclid=EAIaIQobChMI9bHr7pjPkQMVxSXUAR3Jvw2mEAQYAiABEgIrv_D_BwE

a top down bottom up inside mount blind would be a great window treatment. Privacy from the bottom, Natural light for the vanity without adjusting for prrvacy.

https://www.amazon.com/dp/B0DK73Y2CX/ref=sspa_dk_offsite_pinterest_search_1?psc=1&aaxitk=49d787c8a9bf35b3adae3c1bba654c31&tqtoken=AgR4h5zscJNMGSR0Vd-y0-B1eGFmtZR4ETmwAQbVXdM_tS0AGgABAAlyZWNpcGllbnQAC0FtYXpvbkFkc1RRAAEAEWF3cy1rbXMtaGllcmFyY2h5ACRiM2NlMjE3OS0wMzJhLTQ5NTAtOWFlZC00MTczZDMxZmNhMmEAXG7VY19F4X_lKVv8FYQYR3-erLfCgxySSrrsaoftK8nXMwFE6ZdgvB9GW5UIK13ckyb5qbRjXwN6oXq2CvKRF7gDV9lkzQRuZPj64H5HeLArIM4a2OIE0YLrB1hkAgAAEACEGBzAU1KJzQMn2Do3IphcNru9nFUUdwVQZIgBR5NC_gk1J-rmh6giMf2flvicnXj_____AAAAAQAAAAAAAAAAAAAAAQAAABnz_5jY_ZLG2b3f9MB6yNXIEkiHhAdQ4Hi7GMeq1LGYk47u3N5FBRoVxA==&offsiteFlag=1&tag=cashpadpinde-20&hvexpln=apex6

Agree with the two comments above. Looks like you could use two storage medicine cabinets, mirrored in lieu of those you have to house all your personal care products & remove the metal (?) shelf towel rack between. Ferguson online has many in different price points. Paint walls , get new light fixtures & window treatment, perhaps a simple Roman shade. Overall, just simplify. Even IF you keep the chair rail I would paint the area below same as the walls above.

Should the metal on the light fixtures be the same as trim on the mirror ?

Remove that window drape thing. Get some new lighting LED 4000K take all the decor ff the tub deck , take the shlf thin off the wall by the mirrors . A nic ewarm white for the walls smooth not faux finish Some art with very simple frames and nicer too. Simpler mirrors frameless would be nice . The wall no chair rail so all one color. A couple of more hooks for towels and robes . All the stuff off the counter . I do not think painting the vanity would be something I would do unless that same color as the new wall color but in a semi gloss then new knobs too.

Yes, remove chair rail. Paint all of your trim the same color as your wall color. Select a warm off white wall color. (I'd try Ben Moore maritime white.) Try to remove the texture from the ceiling.

Remove all of the arts and doo dads around the tub, no shelves between the mirrors, no drape swag. Get mirrors with skinny frames so the frames are not a main feature.

After you paint and do all else, see if the vanity works as is. If not, then have it painted. I don't think painted vanities hold up well in a humid environment unless you have a really professional factory finish type job on it, which is probably as expensive as getting a new vanity.

Remove the mirrors and the shelf between them. Instead, install recessed mirrored medicine cabinets, and put all the stuff that is currently on the countertop inside the medicine cabinets. (Check to be sure that there are no pipes or other utilities in the wall that would prevent you from putting in recessed cabinets.) Get simpler, more modern light fixtures. Remove all the doodads around the bathtub, and all the pictures. Remove the swag thing and the valence-rod from the window. Get rid of the chair rail and wooden (?) wainscoting and repair the walls. If possible, resurface the ceiling so that it is smooth. Then paint all the walls and ceiling with a very slight off-white color that goes with the tub and tiles. Use 3500K lighting in the new fixtures. Put robe and towel hooks on the wall in some appropriate place (the wall adjacent to the door?). The cabinets look fine to me. If you have "extra" money, you could replace the bright white sinks with ones that match the bath tub and are not so stark, but that will require a bit of work to find over-mount sinks that are the right color, are simple, and will fit your existing openings in the countertop. Looks like a fun project and should give you a good result!