Yes, meant to mention that - that the quickscreen can only be accessed from certain screens (don't really understand the logic of it - not sure why you can get it from the 'plugins' menu but not the 'themes' list, for example).
Also, now I think about it, i guess of course changing the background for the quick menu is something one can do with a theme, including, I guess, showing the volume level. For a moment I thought that would need changing the rockbox code, but of course the quick-screen is already part of the theme engine so isn't that hard to change, at least for players with more screen real-estate.
Maybe will add that to some of my own themes myself.