Well from observation the holograms must be showing a map of the relative positions of where these other cubes must exist. It could be a stellar map of where citadel Ricks had outposts or other important assets that they want to find but don’t want anybody else to find. This is solid evidence that the Rick who killed C-137’s Beth and Diane is associated with the Citadel Ricks paired with the fact that Rick C-137 is the smartest man in his universe that he wouldn’t let rage completely blind him from his analytical prowess and the photo of Killer Rick leading C-147 to where he could find the evidence on the wall of an organization of Ricks to begin with.