I've searched the samples, the developer site, the getting started and the enhancing bla bla bla pages.
Even using some search queries on Google, I can't seem any information on live tiles in Windows 8.
How do I create a live tile in Windows 8? What languages can be used for that? C#? XAML?
Finally figured it out, these live tiles are using tile notifications as noted by others.
Here is the minimal code necessary for updating an existing default tile with a template:
You have to load in a template and adjust it, or produce your own XML code. See the tile schema...
var tileXml = Notifications.TileUpdateManager.getTemplateContent(template);
You need to create a notification, which apparently is an update to a tile.
var notification = new Notifications.TileNotification(tileXml);
You need to create an updater, which will provide you with methods to notify through your tile.
var upd = Notifications.TileUpdateManager.createTileUpdaterForApplication();
If you have all this, you can send an update to the client.
upd.update(notification);