Many times, I see builds that DO NOT fit with the ambiance of the default music. Like a cutesy build in the dark brotherhood house, or a bosmer encampment in coldharbour.
In builds like these, it would greatly improve the 'feel' the builder is going for if they could change the music to the music of a different zone.
Now this next idea is a bit out there, but bear with me. Wouldn't it be great if we could upload sound files for music to our homes?
I've seen a few Harry Potter inspired homes, if they could have used the Harry Potter theme music, it would have made it so much better.
I was in a nightclub/disco build last night, and that place REALLY really needed some techno music.