Here are some tips in conceptualizing your bath’s design:
Lavatory area should be against the wall, or at least be behind a half-wall. Wall mounted fixtures mean easy cleaning.
If you opt for roll in showers, these should have a bench seat. Also, the tiles should slant a bit toward the drain. This keeps the outside floor dry.
Under-the-floor tubs should be built with a raised area, and not steps. Handrails should also be built into the wall, for safety.
Heating sources like heat lamps or exhaust fans should be installed near the open shower.
If you put up windows and skylights, these should be proportional to the total area of the bathroom.
If your bathroom is small, install full mirrors. These can make small baths look large.
Functional areas should be properly lighted.