It is already, in the filmstrip located at the bottom.
The dot is displayed on thumbnails, not on full images, so you will see it just in the Grid and in the Filmstrip, but not in the Loupe, Compare, Survey views, nor in Book, Print, Slideshow and Web modules.
What Marco said, just make sure the Filmstrip isn't tiny, because badges get hidden when the size has been reduced. If you hover over the top of the Filmstrip, an up down arrow cursor appears. Click the top to the Filmstrip and drag to change size.