This is the finished model of the alien bathroom. It depicts the key aspects of the design necessary to promote a feeling of security with the alien lifeform.
The interior walls are made of a generic stone meant to be familiar to the alien. The interior can be flooded with any color of light, any gas, and pressurized to approximate the environment of the alien's homeworld, if known, or judging from the alien's physiology. The bathroom environment is monitored and adjusted from the control console on the roof of the room. The toilet itself consists of an arrangement of padded arms that can be positioned as necessary to fit the alien's body structure. As a generous gesture, the alien's waste is removed through two drains and a vacuum system. De-scenting systems have also been arrayed around the main drain.
Ideally, this system will create a secure environment in which the alien will be comfortable to attempt a means of communication after it has done its business.