Additionally to the notification Quassel already provides I would love to see a second type of notifications.
It would be great to get "room notifications" for some rooms, ideally the user can define this per channel. A room notification would create a short notification for every message in the given channel which would result in a "notification bubble" with the message but no further permanent notification like a blinking tray icon because this kind if notifications are not that important.
Rationales: Beside the existing notification system which notifies the user if something happens directly related to the user, e.g. if the user was mentioned, it would be great if the user can monitor a chat room in the background. This would enable the user to do something different and still keep track of what happens in a channel by getting short notifications about every action on which he can decide if it is interesting for him or not.