Don't make the image too dark or pixelated.
Avoid bright, vibrant colors.
Don't make the creature's face look funny or cartoonish.
Avoid adding distracting background elements.
Do not use very soft or delicate strokes that minimize the grotesque appearance.
Avoid a friendly or happy facial expression.
Do not make the image look childish or cute.
Avoid overly complex details that make the image confusing.
Don't let the creature's skin look too even and healthy.
Avoid perfect symmetry on the creature's face.