How about having a ton of inhabitants, and making them exhibit swarm behavior? So when you're walking around they mingle around, react to your presence, etc. Make the map look a bit like the xkcd virus aquarium!
I think it'd be fun to look forward to connecting to such-and-such island because you want to see how that changes the inhabitants' behavior based on what's on the island, perhaps? (It's not thematically appropriate but I already want to finally connect to Amusement Park Island because it'll make them go nuts. All the blue inhabitants tend to stay at home a lot, but then you add Library Island and they start hanging out there, which is cute?)
To make it more interesting to watch, how about a day/night cycle and different preferences of where they want to be based on time (fun concept: when you're zoomed out, a fast-forward button that's only there to let you see the large-scale-time behavior).
I hope this sort of suggestion is welcome! Have a nice day, Marcos!