I don’t expect everyone to have a professional headshot, but it’s 2011. Digital photography is the norm. Every cell phone has a camera built into it, and digital cameras have been used for the past decade. Surely, on some hard drive somewhere, there exists a nice photo of you somewhere you can use as your avatar and profile photo.
Find someone whose opinion you trust and who has a good sense of style. Someone who wants you to look as good as possible is usually best for this task, but anyone whose opinion you trust helps. Ask them if they like your avatar.
Don’t get pissed off if they don’t. Remember, you ask this person to do you a favor, and they probably just want you to look good. They aren’t judging your look, just a photo represents you. You can always ignore their opinion, or change your photo with a few clicks.
Also, if this person has an abnormal sense of fashion, such as they dress like pantaloons are still hip, take their opinion with a grain of salt. You don’t need your avatar to be an animated cartoon that flips the bird on everyone. Just a simple, nice representation of yourself.
And for the love of social networks, smile. There’s nothing more depressing than logging onto Twitter/Facebook/LinkedIn/Whatever and having to look at a sea of frowning faces that look like they’d rather be anywhere but a society where they can spend the entire day on the internet watching cat videos. Online life is good people. At least pretend to enjoy it.