For avatars in general, consistency is preferred imo.
I'm a visual learner, I can't remember all the vague and similar-sounding usernames to save my life, so the avatar typically is the easiest person(ality) identifier.
My own avatar, well...it's me!
It's me while drinking whiskey around a hotel courtyard fireplace, mean mugging the friend that caught me by surprise with her camera.
Why a photo of me?
I hit a point not too long ago where I contemplated the fact this no longer our fun geocities, midi, a/s/l Internet of 2001 that we grew up knowing and loving. I figured putting my actual face to the profile could lead to a momentous positive change in forum culture. Removing the animosity from message board posting will help us come together in these divisive times and be more excellent to one another.
Obviously that is not happening (yet!), so at least the lack of animosity on my own profile keeps me from too often falling victim to the appeal of being a total sarcastic jerk (
especially on gameday threads).
P.S. @Angie, I do love the Mabel avatar, it brings joy to even the most contentious threads here on CF. Gravity Falls is one of the most overlooked, underappreciated shows of the past decade.