"The Black Cat" and "The Tell-Tale Heart" do have definite similarities. I like your idea about relating animals and animal-like characteristics to evil and homicide. One major similarity that you could use in correlation with your idea is that both stories feature an unreliable narrator and the theme of insanity.
Poe uses the unreliable narrator to force the reader into the uncomfortable role and perspective of a mad man. In "The Tell-Tale Heart" the narrator does relate animal characteristics to things through his maddened view. The narrator reveals his fear and loathing though his repeated use of the phrase "vulture eye" to describe the old man's eye. In this case, the unreliable narrator's fixation on an animal attribute led him to madness in homicide.
In "The Black Cat," interestingly enough, Pluto's damaged eye, caused by the hand of the unreliable narrator, also becomes the focus of his increasing madness. His guilt at having caused such a wound and his anger at the cat which he blames for having made him do it, coupled with the fact that the cat now avoided him drives the narrator into a fit of rage. Later, when the narrator gets a new black cat, it too is missing an eye. Coincidence?
Another similarity between the two is that both of the unreliable narrators choose to hide their victims within their home. The body of the old man is chopped up and hidden beneath the floor boards, and the wife is chopped up and concealed in the wall of the basement. Moreover, both corpses 'reveal' themselves through mysterious noises; the narrator in "The Tell-Tale Heart" hears the beating of the heart, and in "The Black Cat," the narrator hears a horrible wail when he knocks on the wall for the police (which of course is the second Black Cat. The narrator had "walled the monster up in the tomb" (8).