One of the more interesting creatures we heard about - but didn't see - was the red-bellied snake, which interested us primarily because it eats slugs. We have armies of slugs here, so slug-eaters, especially slug-eaters who don't want extra helpings of vegetables, are welcome.
We'll probably be adding some more rock piles to the landscape. Even if we don't attract red-bellied snakes, which I've never seen here, they'll be good for other snakes as well.
We have quite a set of predators here that we're hoping to encourage. The cats feast on various rodents. The dogs seem mostly good for scaring things off, like an occasional deer, if they're awake and notice. (Sprocket does help the cats sometimes, though.) We have garter snakes in pretty large quantities, and I remember seeing a big snake eating a still-kicking toad a couple of years ago. The chickens aren't vegetarian - they love eating bugs!
I'm also planning to finally get my bat box installed this spring, which will add some flying predators to the mix.
We do worry about predators who'd like to eat our chickens and ducks. We know there are foxes, skunks, opossums, and racoons around, and we hear coyotes occasionally. Bears have moved to within a few miles of us, and may prove to be a challenge eventually.
It's going to be an interesting ecosystem, and will probably give us the occasional headache - but it still sounds like a lot more fun than the usual just plain garden.