Not that I disagree with the main point here that headliners are usually well-known or well-sought after animal, but I dont think it has to be the case every single time. I doubt any laik can tell that the weird bear on SEA pack cover is a sun bear or the horse is a wild Przewalski horse (I was very surprised to hear alot of people, and even people that play PZ alot to refer to it as "just a horse" and then they procceed to say they dont understand why is everyone excited about a horse). I doubt average Joe knows the succesfull reintroduction story of the Wild Horse really and their importance as a Zoo species.
I agree that the species should be interesting and different enough from the other headliners, thus I did get why the Amur leopard was not a headline of the Conservation (too similar to jaguar from SA), but that is the only requeirment I really see as needed, especially now that the big ticket animals are mostly present in game. I think things like Sloths, Porcupines or Emus would potentionaly be headliners, but on the other hand I dont understand this community obsession with "headliners" and the forever present fear that we dont have enough "headliner" animals left for the packs to continue. That is really absurd.