Do I have to wait until I've been a member for so long until I do it?
Nope you can change it right away.
Changing My Avatar and Profile Picture will help you.
MarkEX Community Manager
Nope - here ya' go: https://excommunity.becomeanex.org/message/214176-re-profile-picture?commentID=214176#comment-214176.
You may have to log out and log back in for it to take effect.
Let us know if you have further problems with doing it!
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