On powerpets where are all the backgrounds I have the Graveyard background but I can't find the Beach Forest and Winter?

The winter background you can get from doing Tumid's Quest. It may take a while though, so just keep on doing the quest.

How do you find the graveyard background?

The graveyard is retired, it was in the tree in Northern Woods where Nova hides.

(REVISED ANSWER) The grave yard is brought back occasionally in October... this year it was also in the tree.

The beach background can be found by doing the shark quest.