Just a small suggestion.
Once a knight has reached the vanguard rank (or a knight on that account) the Jukebox will be available. When said knight is in the ready room, the "Activities" tab will have a button labeled "Jukebox" at the bottom. The UI of the window opened when the button is pressed could be something like iTunes or whatever OOO would do. The function of the Jukebox is to play whatever SK theme you want at a rate of 750cr(Not sure) for two minutes. The music would just be like Wasteworks, Undead, Treasure Vault, Aura Isles etc.
Also, maybe add a small bloop or ping sort of sound whenever you get a personal message. This would be toggled on/off in either the Chat or Game section of the options(esc) screen.(This is probably more likely)
For the jukebox, it's a nice idea to allow players to change the music. However, forcing them to pay would be a bit over the top, since I can get the same effect by just turning down the volume in-game and listening to iTunes for free (which is what I do now anyway.)
As for the bloop sound effect, it seems legit. +1 as long as you can turn it off.