Different types of animals, maybe some new Glitch species. There could be a little thing beside the enclosure that you select and it brings up a few things (facts) about that animal/species.
There could be activities and things to do that boost your mood. Maybe there could be a playground :)
Quest: an animal has escaped from the Zoo! Find it and bring it back!
-- You would have to go searching for it in streets and maybe buildings and then bring it back.
Or it could be a group project thing.
Zoo island!
Just an idea..