Likeness is the resemblance of a person. It could be of an actor, athlete, musician, etc. You might be using someone's likeness if you can recognize who the person is from the artwork. Someone's likeness is generally covered by publicity rights.
When submitting fan art depicting a character from a movie or TV show, you should focus on what makes the fictional character special, not the actor who plays the character. It's best not to include recognizable features of the actor themselves, because that could be using that person's likeness in an unauthorized way, and we may have to remove your artwork from the marketplace. Just remember that the partner may own the rights to the character in a movie but not the actor who happens to play that character.