Eh, mine is simple and silly. I use it everywhere these days.
It's from an old Newgrounds series (you can find it on YouTube these days much easier) titled "There She Is!!!". It has no words, only delightful non-English music. It tells the love story of this bunny rabbit here who chases the kitty cat in order to get him to fall in love with her and have them date. This takes place in a world where rabbits and cats aren't allowed to date or marry and is seen as something akin to a massive sin.
It's a good series, I recommend at least a single watch.
Anyway, the reason it's my avatar is because as I've grown up, I've realized that I'm the cat to an extent. Just living my life, doing my own thing, and then some random thing happens that turns my life up-side-down and I have to learn to deal with it. It's also how I approach my love life to an extent. I don't really ask women out. Mostly because most women just... don't impress me much. But, the ones who decide I'm worth something and chase me, tends to make me sit up and take notice. In any case, the series reminds me of how I approach my love life, which translates to a decent chunk of my personality. So, I can relate, so I have the picture.
Also, I think it's freakin' adorable. Oh, and it sometimes fools people into thinking I'm a girl, which means they're less likely to burst into insults and being rude upon interacting with me on the internet. At least, until they figure out I'm a guy... or figure out that I don't pull any punches.

It results in a lot more politeness towards me.
In any case, it's from the second episode of the series, titled, "Cake Dance". Kitty brings her a cake for her birthday and basically endures terrible and annoying things just to get it to her. And she tackles him and gives him a Public Display of Affection to which he just looks like, "Seriously? Fine..."
It's me all over. So... that's my avatar. Like... everywhere. YouTube, Facebook, here, anywhere they let me use it.