My temporary default. I'll get bored of it quickly. I saw the picture from the cover of Freedom of Choice in the liner notes to their Greatest Hits which I bought recently and thought that it would make a good icon. The text wrote itself, of course, so you can't blame me for it.
These are the ones I use in the majority of my posts and comments. They're all of Cat from Cat and Girl, and I use them like mood icons, especially in comments. From left to right: my usual default, deep in thought, doubtful, either hipster poseur or music geek depending on context, and happy. (Cat is happiest when eating paint.)
The "hip" one there is one of my favorites. I need to find a better picture of Cat eating paint with a suitably happy expression and a grey background instead of black.
I've met a handful of neat people on here solely by noticing they have an icon from Cat and Girl.
This picture of Dick Feynman is from the cover of Six Not-so-easy Pieces, the second collection of lectures excerpted from the Feynman Lectures on Physics. One day I glanced at the cover and noticed that the size and ratio of the photo was awfully icon-ish, and scanned it. I'm not the only person to have noticed this, as I see other scans of this icon showing up occasionally. I admire Feynman a great deal.
Various pictures of me. The first one is there because I like to have one icon which is a normal photo of me for people who look at my userpics page hoping to find a photo. It's about a year old, and I've lost a bit of weight since then, but it's pretty accurate. The second one is me recalling Hunter S. Thompson. I don't usually wear the hat and the glasses together. Lastly is my Christmas icon, which inspired a few other people.
It's a tradition in LiveJournal Support to have an icon that somehow involves a bunny, referring to the support slang "bunneh" for someone that gets to a request while you're still reading it (and who is thus "quick like bunneh"). This one is part of bunny headphones by Kozyndan. I hope to get a Kozyndan print or two on my wall eventually.
S'all she wrote.