Work it out as a concept by asking yourself logical questions and 'translate' the answers to an image. Question: Who's abusing animals? Humans. Why do humans abuse animals? Some do so because they are mean and enjoy it, others because they are ignorant. Can animals defend themselves? Most of them are smaller and can't defend themselves.
So a human could be represented by a gigantic scary hand and the animal as way smaller and afraid. Make the big bad hand project a long sinister looking shadow over the animal. Maybe you can add a "Do Not Enter" logo and place it on front of those images. (you know the red circle with the diagonal line), etc.