As a user I'd like to control the audio when at the lock screen.
Take the scenario where you were playing music on your laptop, possibly to a peripheral which would make you turn up the volume to such a level that it would be playing out very loud from your laptop speakers, and you put it to sleep to later have it wake up when in a hury to access information or some functionality. Take a business meeting or a college lecture. In this case you'd want to take control over the audio quickly enough to prevent a unconvenient situation.
I'd like to see the ability to control volume and mute (ofcourse also with the media keys), and preferably something like on a lot of smartphone's lockscreens today; the ability to play/pause/etc whatever media player(s) the logged in user(s) are/is running without having to unlock.