My personal thoughts on the most important animals (animal groups) left:
1. South american primates: at least 3-4 - Howler, spider, squirrel, golden lion tamarin
2. African primates: baboon and at least one typical old world monkey from Africa like the mantled guereza
3. Indian primates: just one would be fine, with the grey langur being the most basic but important option, lion tailed macaque being a more exotic yet interesting alternative
4. More small cats: ocelot, Palla's cat and serval
5. A coati (SA i think is the most important one but any would do)
6. Indian ungulates: at least blackbuck and muntjac, you could throw gaur and nilgai as well but i don't deem that really necessary
7. Patagonian mara: Patagonia is empty and the mara is an extremely common, versatile and docile animal.
8. Habitat birds: at least another crane (grey crowned crane of course), greater rhea (the last ratite and important for SA), a stork (marabou and white stork being the most important), ducks (at least one), more galliformes (helmeted guineafowl, golden pheasant, wild turkey and cappercaillie at the very least), a spoonbill (roseate clearly), an ibis (scarlet and northern bald ibis), a pelican and the secretary bird.
9. Caprids: the only one i deem important enough is the markhor, but chamois and mountain goat fit as well.
10. The bears: spectacled and ABB to finish the entire group at a species level
11. Walrus: maybe rare in captivity but just like pelicans, ducks and bunnies a very recognazible and popular animal.
12. Lagomorphs: i prefer the wild kind but any would do.
13. More habitat reptiles: african spurred tortoise (radiated and red footed are also good options), habitat turtle (Arrau river turtle being my prefered one but there are other options), an australian monitor (like really, how come we haven none?), and an african croc (Nile, please)
14. A handfull of oddities left: tree kangaroo, tamandua, aye-aye, short beaked echidna
These are not my personal choices in all cases. i can live without a walrus for instance, but i think those are the basic animals that we really need right now.