OOH: this is the symbol of the Order of Hermes from Mage: The Ascension. It used to be my default icon, no, I don't use it much anymore. If I'm talking about Mage or Ars Magica I'll still use it.
SOE: This is the symbol of the Sons of Ether, the mad scientist types from Mage the ascension. I don't know that I've ever used this icon, actually.
fez: This is a picture of me from when I played in the LARP Six by Nine. It's the only icon that is an actual literal representation of me, and I tend to use it when I wish to convey sincerity and seriousness(even though i'm wearing a funny hat)
Teeny Little Super Guy: Well, it's the teeny little super guy featured in segments on Sesame Street. I tend to use this one for either silly things, or congratulatory things, 'cause he's dancing. :)
Spider Jerusalem: Spider Jerusalem is a character from the comic book series "Transmetropolitan." He is essentially Hunter S Thompson, in a transhumanist future. I use this one when i'm talking about something that pissed me off. Or Transmetropolitan.
Nonstandard Spacetime: This icon is taken from a bunch of wierd warning signs. I use it rarely, usually either when i'm being silly, or talking about weird crap.
If you want to continue the thing, post in the comments indicating your desire to do so, and I'll pick six of your icons for you to explain.