So far I've had the most success with a simple picture of me stretching when I was tired one morning and sister had my phone and was bored. I think the main feature is that you can see my forearms are veiny. But most of my face is obscured by sunglasses, may hair is covered by a wool hat, and I'm generally being tired, sleepy, and uninteresting.
Pic in question: http://instagram.com/p/lm5FNjkxp1/?modal=true
I made http://tinderus.com/ the other day, essentially just to give people an alternative perspective on their profile and images.
You can read about it here: https://medium.com/p/8e02c9a3c33b
I run http://catchlondon.com/ - a PR Agency focused on technology that I founded one year ago.
http://www.psychologytoday.com/blog/the-social-thinker/20100...
You could even push that concept further, and test a picture in different cities/countries. That way you can find where in the world people find you most attractive :D