If you frequently use Gnome for chatting through Empathy, you might have come across a bug which shows the tray background when a banner pops up. Recently, this bug has been fixed by Ana Ris, a developer working on Gnome shell.

Ana writes -

“In my opinion, the suggested bug makes sense, since currently the roles of the pop up banners and the message tray when a notification appears are somehow blended and the message tray takes up also the role of popping up on events.  Therefore it should rather remain faithful to its main purpose, which is providing an uniform concept for providing information and awareness for different events that is controlled by the user. “

A screenshot of the message tray when a notification pops up:

And when it gets expanded:

Looks elegant. Ana is currently working on implementing a close button on banners and relative positioning of message according to importance and parent.