Toribash songs
If it still works the way it used to (I don't have time to check) then adding .ogg music files into /data/music/ and naming them track# will automatically add them to the game's playlist.
It then played through them in sequence, though I'm pretty sure there was a limit to how many you could add, plus there's no way to switch to the next track etc, so that'd need added to the client.
As for more music... Well if people made more, and it was made specifically for the game then it'd give something to jam under hampa's nose.
For the moment you could pop your own in there.