Language and meanings of words in Animal Farm also reflects its evil. The powerful animals manipulate words to further their own agenda. Snowball is able to explain anything with his fast talking. When the birds object to the motto, "Four legs good, two legs bad," Snowball explains that the bird's wing "is an organ of propulsion and not of manipulation." Therefore, the wing is considered a leg. Squealer, the head of propaganda for the animals, "could turn black into white". He twists words, even to the point of changing events of the past. Truth is relative in the novel, depending on who's talking.
The theme of good and evil is also seen in the lack of equality among the animals. They begin with the idea that all animals are equal, but it doesn't take long for the pigs to elevate themselves above everyone else. The seventh commandment is changed to read, "All animals are equal, but some are more equal than others."
Though the evil in Animal Farm is not as obvious as it is in Lord of the Flies, it does exist in the form of ideology and politics. Just like any totalitarian government, the animals ignore the basic human rights of all of the animals. In Lord of the Flies, the evil is represented by Jack and Roger. Ralph, Piggy, and especially Simon symbolize the good in humanity and are punished by the forces of evil.
Good luck! It sounds like you've got a great start!