Is it possible to change icon in tray on Play/Pause action?
Yes, actually. It's a bit fiddly because there isn't a "rhythmbox is playing" icon. OTOH, there's a Gnome "playing icon" and the rhythmbox icon which I can combine to do things.
Add play/not-play icons, fixing #2
You can use two different icons from rhythmbox, without Gnome "playing icon".
rhythmboxIcon = "/usr/share/icons/hicolor/32x32/apps/rhythmbox.png"
playIcon = "/usr/share/pixmaps/rhythmbox-small.xpm"
Here is a my patch.
Status icon looks cute for me now. Thank you.
True, it could be done like that but I'd personally find it very hard to tell which one is the playing icon. This way you get an unambiguous play icon.