Click on the first thumbnail. You can then go directly to the next image by presing on the ">>" link.
The template TemplateTrails-ImageTemplate.
You can see Sandbox 5 where the $PrevThumb and $NextThumb variables are used to display the previous and next thumbnails in the trail.
See also Sandbox 6 where you can display a small trail of all pictures below the current big picture.
At Sandbox 7 is explained how to select alternative ImageTemplates.