You could follow hotel ideas and put a coving around the ceiling with lights hidden in this. Or a central feature panel with the same lights in but it depends how tall your ceilings are?
That can create a nice cosy effect.

Also faux window panel with natural led behind to make it feel like natural light. Could work.

Otherwise lots of mirrors and wall lights perhaps to reflect light around?

We looked into loads as was planning a windowless bathroom but we managed to get a rooflight in as not a flat.

Just had the windowless bathroom in my flat renovated and very happy with it. I chose to only part tile and painted the rest of the walls white, which has definitely brightened the room. Using wood effect LVT flooring has warmed the space up and was a great idea from my bathroom fitter. I only have one light in the room, but bought a smart led, so I can change it from a bright white light to a warmer yellowed light. Really great for relaxing in the bath. Good luck with your project!

Use indirect lights behind wall panels as well as behind mirror use warm white light it ll be more bright

do you have a picture of it?

This type of lights u can put also give me layout i ll give ideas and there is no wall for window at all?? R u gonna put exhaust fan?