To add credibility and life, it helps to have believable proportions, articulation of the character's body forms regardless what style or genre.
I've created some notes to keep in mind when developing your characters.
To create subhuman or superhuman characters, it's important to know what the normal human proportion is. From here you can distort and see how different relationships create different impressions of the body to the head size and body parts to each other. Hope this helps in your explorations. :]
Gesture - The big relationships of the forms of the body. The Gesture can be described as a flow of line through it's parts relating one part to another.
Iconic shapes for female and male figures helps simplify the genders in character concepts.