Actually, the bird bath idea gave me a idea...Mom's made a few new 'friends' in the form of a turkey colony that has been visiting-and sometimes staying- in our yard. She tosses out cracked corn and stale bread for them, and now they've gotten pretty use to our scheduals...
If the next expansion is animals, and they include wild ones, it would be cool if birds like canaries and pigeons and finches were catchable, or at least you could attract them to your yard with food or items. Depending on the food, or if stuff like trash was left out, other animals could also be attracted, like raccoons, possum, skunks, bears, and deer. Deer could be a nusiance for gardens with short fences, skunks could spray people and pets, bears are incredibly scary, and possum and raccoons could be aggressive or submissive to dogs and cats.
Also, I read about pet's personalities on the Sim wiki, and it would be nice if those were extended, to things like Nice, Mean, Shy, Naughty, Naive...So on and so forth. Finally, it would be nice if there was a shelter or pound, to adopt premade or randomized animals instead of making your own. This could also give a bonus to 'Good' sims. Of course, pets from the pound might have negative traits, from being in negative homes...But a 'retraining' happiness points award, or a special training area for pets and owners, could take care of these bad traits, and gives you the ability to pick different traits for your pets, acting like the happiness points reward "Midlife Crisis" dose.