There are a number of ways you can customize the look & feel of your notifications:
To change the overall look and feel of the notification, set the Skin property.
To change the content within the notification, set the Text property, the Title property or add controls in its ContentTemplate.
To change the way the notification initially becomes visible, use the Animation property.
To change the look of an individual aspect of the notification, use its CssClass property and set up CSS styles as needed.