I would love to see more South American animals. If I had to choose eight species for a South America pack, these would be my choices:
Black capped squirrel monkey (Tropical) - This is a representative species for the Amazon rainforest but would be a good addition on account of its small size; they are larger than a meerkat and so should be workable.
Black necked swan (Aquatic, Grassland, Taiga, Temperate) - This is a commonly kept bird that lives in the cooler southern parts of South America; they would add another species that could be kept in a relatively small enclosure and has great ornamental value.
Capybara (Aquatic, Grassland, Tropical) - There are easily half a dozen different types of rodent that could work as habitat animals, including agoutis, paca and maras; this one is the most-wanted by the community and is one that I wouldn't mind seeing myself.
Chacoan peccary (Desert, Grassland) - This is an endangered species found in the very arid Gran Chaco region; they were first identified from fossils before being found alive and they are now increasingly being kept and bred in zoos.
Northern helmeted curassow (Temperate, Tropical) - This is one of the more endangered curassows that is still commonly kept in captivity; they live in high subtropical cloud forests in the northern Andes but are often kept in more standard tropical spaces as well.
Six banded armadillo (Grassland, Temperate, Tropical) - Armadillos are a group of animals that evolved in South America and should definitely have a place here; I considered the giant armadillo but, on finding they have never been bred in captivity before, I went for a smaller, more commonly-kept species.
West Indian manatee (Aquatic) - I just can't see a full pack of totally aquatic animals coming, to be honest; this would be one of the best places to add this species, which is a good representative of the Atlantic coasts of South America.
Surinam grasshopper Tetrataenia surinama (Tropical) - Not only are these a very beautiful grasshopper (as seen below) that are fairly close in size to the Lehmann's poison frog, they also tell an important conservation story, as this is a species that naturally moves into areas of forest regrowing after logging.