When planning bathroom lighting design, you need to think about two things: how the space might look in the daytime and the nighttime.
During the day, it would be nice to let in as much natural light as possible without sacrificing privacy. Windows are typically small and higher than the average user height. However, you can also make them bigger and lower if you use privacy curtains.
One of the windows should be near the mirror of the bathroom sink to illuminate the face of the occupant. Lights can also be positioned around this mirror for the same purpose during the night.
It would also be wise to install two ceiling lights. One of the for the shower stall and another for the rest of the bathroom. If your space is bigger than average, then you can add even more pin lights.