While I personally doubt the level of type correlation, I thought I would at least test the hypothesis here.
I was told by my peers that I have a fairly high number of casual or candid photos of myself, in which I have a hand/fingers resting around the area of my chin. This habit has also been pointed out by my friends at other times as well.
If it is type or IE related, I would be inclined to think that it is more frequent amongst Intuitive-egos (perhaps Ne > Ni) as it may loosely deal with somehow stimulating physical sensations (Si) while being lost in thought.