If you want to see the representation of an object, then you can change in the same place as the display, the layout. Pick thumbnail view and that will show the thumbnail of the representation.
If you have used a media metadata element instead of a related object representaton, then I am not sure what you need to be specially to show the thumbnail for this, but you could try adding .icon or .thumbnail to the end of the display template for it. EG. ^ca_objects.media_element.icon