This idea is to add additional sounds and background music to the user interface.
Currently (as of version 2.86), we have an opening splash screen sound, sounds for people (male, female, dead), sounds for vehicles (moving, break down, maintenance), and a sound for settlements.
We could use more sounds for people based on their current activity.
Any sounds we use will have to be copyright licensed in a way that is compatible with a Free Software project.
A good place for finding sounds or base sounds to work with is The Freesound Project
There's discussion on adding a background music loop. Another possibility is dynamically-generated music based on the events in the simulation. We should consider the amount of CPU processing for either of these options, of course.
Feel free to add more ideas to this page or add to its discussion.