When you have a game offer in the list and someone accepts the game there should be an audio notification. I'm thinking something like the challenge notification.
 
Reasoning is that sometimes I have to wait quite some time for someone to accep a chess960 game and if the window is in the background I often miss it.
 
-Damon

I suggested the very same thing some time back. The challenge notification seems to work even if the window is minimized, so something like that would be perfect. I, too, miss tons of games by having the Caissa window minimized while waiting.
 
-f

This is on the to-do list