Please post 1-3 photos of yourself (I'm most interested in the face for still photos) with natural expressions. By "natural", I'm hoping first for expressions that are genuine and not forced, and then another possibility is an atypical face/pose that, even if it seems weird, is an expression you make ALL THE TIME (according to observers). If you want to post a "straight face" that's actually the best IF you can do it without tensing. Real natural please.
Then I'll compare them and point out why they are "ISFP". I welcome others' comments on this, too.
This was suggested by Quinlan.
Starting with the EYES... Notice how most ISFPs have about 1/2-1/3 less space between the eyes than we're "supposed to,"* they're usually fairly almond-shaped (and though I've seen exceptions, they're usually not THE BIGGEST eyes you've ever seen), and most noticeably to me, one eye is always obviously higher than the other. The only time the eyes look "level" is when we cock our heads to the side (we often do this). Other types will cock their heads to the side and make their eyes UNlevel, but when we do it, the eyes actually become level (or if we tilt our heads the OTHER way, our eyes are at an almost comic slant).
Next, the MOUTH/SMILE... I haven't proven this to be ISFP-ONLY or anything, but I do notice that half-smile thing (as Quin pointed out), and the weird thing is that the side of the face that smiles the most (tightest muscles clenching) usually corresponds to the LOWER eye on the face, as though we favor that side.
More later as soon as I get a second to write. I want to comment on the nose and jaw, too... maybe even the eyebrows...
*The average space between two eyes is the length of an eye.