When you're planning a stuffable animal themed party, you have a few options for your setting. Some parents opt for one animal choice, to avoid fighting over specific animals, while others prefer offering an array of options to the kids. If you wanted to go for a particular theme, then you could choose a few options that relate to it. Alternatively, if you want to keep it generic, you could offer a wide variety of animal styles.
If you have a myriad of animals, you can go with an overall farm animal theme. This is probably the easier option, as it gives you more options for party favors, snacks, and games. Go with the color red, it's often associated with barns. Give the setting a farm feel with cornstalks and hay bales.
If you want to go the other way, and keep everything the same, choose an animal that you can work with. For example, if you offer one choice, opt for a bear. Your child could have almost any theme decorations, and a stuffed bear section would make sense; it is versatile.
Regardless of the decor and theme, your party will need favors. Offer animal shaped treats or cookies as snacks to take home, this is a good idea for favors because they're already taking home their stuffed animal, so a snack feels like a new treat AND it's cost effective. We can't promise other parents will love you for feeding their kids sugar, and then sending them home with sugar, but you'll be the coolest parent ever.