Haha welcome to AO. Don't be shy on the forums, and if you ever feel threatened by another member, you could always PM a mod about it, or even me if you want. Generally speaking, the a$$h@)es don't last very long on this forum, 'cuz the mods here are pretty darn strict (so make sure you read and follow the rules). Other than that, enjoy your time here, and have fun! We need more active and contributive members on AO, so please stick around. =]
About changing you avatar, I think you'll have to stick with the custom ones until you're a community member (i.e. you're a member for more than 30 days you've got more than 100 posts). You should be able to upload your own after that.
PS - don't overuse the ellipsis.