I use my subsonic every day and so do many of my friends and family to stream music at work.
I thought it would be nice to have a message area on the main screen that you could use as the admin to post messages regarding what ever you want, such as server will be down for maintence on such date, just added new "kid rock' cd, etc....
I also thought that it would be nice to have an integrated email system that would allow you to store your users email and be able to send out an email to all users for some what of the same purpose as stated above.
I think it would also be cool to have a user modifiable interface for customization. Nothing complex, i do understand i can modify the theme a bit, but maybe have a section where you could upload a personal banner/logo in place of the subsonic one to allow users to make subsonic a little more personable.
Let me know your thoughts likes/dislikes?