Research

During earlier research into psychological thrillers, I found the use of bathroom scenes impacted on and had a lasting effect on me because of its successful creation of tension. Within a bathroom are mirrors, dripping taps, water and steam which all can be used as chilling props to create the perfect location for supernatural, criminal or shocking events.
The steam could be used to mask or disguise an enemy, create an eerie mist/smoke like effect to blur what is viewed in the setting. Water 

Shots and angles can vary greatly here to reflect the mood of the scene or emotions of a character. Mirrors are commonly placed in a bathroom scene, this allows a character to look at themselves, reflect for a while and could sometimes be used so that the characters true emotion come through their facial expressions and body language. 
The first example shot is an over the shoulder to view the back of the character as well as the front of their body in the reflection. This can give an effect of spilt personality or split conscience as a character reflects.



Perspective

Shots are effective in giving different perspectives of a scene, mirrors are often used to portray a perspective usually within horror or thriller films.
Certain characters may have a different perspective to what the audience see, this can be created through special effects or just by the specially placed angle of a shot. A popular example would be someone standing in the corner or the room or behind the oblivious character. The audience may see this through the reflection of a mirror. 
Another perspective is where the camera is used as a mirror, an example here taken from Donnie Darko, the character will keep eye contact with the audience, and act normal as if looking at themselves, this could show how a character truly feels when they look at their reflection and impacts the audience personally with direct address.