The imgur chrome extension adds small icon right next to your address bar which can bring up a smaller version of the imgur gallery.
The icon is also being used to notify you when one of your captions has been commented or someone sent you a message.
In these cases the dot over the "i" changes from green to red.
When clicked on, the icon reveals a small window showing the latest 16 pictures, ready to be clicked on.
Users are not notified about new images via the icon.
Notifications are updated every minute
The gallery is updated once in 5 minutes.
Simple, yet effective.