Master bathrooms
The design and functionality of master bathrooms vary widely. Some are relatively basic, while others have a whirlpool or other features. Some are even divided into multiple rooms! You just have to decide what features you want yours to have!
Commercial restrooms
When designing commercial bathrooms, two major factors to consider are privacy and sanitation. Privacy is usually solved one of two ways – for single stall restrooms, a lock on the door; for multi stall restrooms, locks on the stall doors. That way it's easy to tell which stalls are in use.
As far as sanitation is concerned, one feature that will help a lot is tile floors and walls, and a drain in the floor. That way, you can just bleach and hose down the entire bathroom on a regular basis. Any feature that will make sanitation easier or simpler should be given consideration.
Of course, durability should be a given in commercial bathrooms. People will treat fixtures roughly, so they should be built to withstand the abuse.
Kids' bathrooms
If you're designing a bathroom for your kids, the main factors you probably want to consider are safety and durability.
With safety in mind, you should consider to as much as possible use non slip surfaces. Also, kids WILL spill water in the bathroom, so try to design the bathroom in such a way that spilled water will not cause damage or a safety hazard.
Durability is pretty obvious, for the most part – minimize glass and other delicate decorations and fixtures.
