This happened to me too. I was all excited that my winter petopia had a pet cemetery, but then the Halloween images disappeared. My winter petopia showed up right away without my having to exit the game or anything
Here is my current petopia village. I love that the pets skate on the ice! In the Halloween petopia you could throw the pets in the water and they turned into skeletons.
Lol yeah but it was more fun to throw them in the water and watch them turn into skeletons. You know not one of my rescue paramedics ever tried to save them? I figured maybe the rescue helicopter would pick them up and take them to the hospital, but nope.