Hihi, Myl here, creator of Hacheeachkee
I'd say if you have a mascot in your comic or a character that shows up a lot in your comic or one that you identify with most can be your Icon, I usually call Icon's "Avatars", so profiles are the best options in my opinion as they show who you are or represent.
If you are going to be on the forms much I'd advise spending a good amount of time on it as that is the first thing fellow members would recognize you by.
For example, I've only been on the forms for 2 days and I keep seeing this person's avatar: Uzuki You might have seen it, big toothy smile, face all up in the camera boundaries of the Icon. But I'm sure a lot of people are clicking on that face, and indirectly, clicking into Uzuki's comic series.
Talk about first impressions...
Good luck!