LiveJournal userpictures

Hello! I've been lurking around here, posted only one tutorial, but I need help now. I'm not sure if this belongs here, but it's the only place I could think of that I knew I'd get help.

Okay, so I have a userpicture. When I change it, it automatically changes on all my posts and comments. But I've seen a lot of people don't have the same userpictures everywhere. One post has one, another comment has the other, and the third comment reply has a totally different one. How do you do that? Is it a paid account thing or is it possible to do without having a paid one?

I'm sorry if I don't make sense. It's 7 am.