Answer and explanation
I took this self-portrait as an attempt to capture an expression which conveyed Ti. There were a few extreme impressions people got from the photo, which was an amusing surprise. The computer programming language inventor vs. serial killer test was especially amusing since I write software for a living.
The photo was taken indoors with existing window light and an artificial tree, but I did try to make it appear to be outdoors just to be more interesting and add to the mystery somewhat. The camera was a little below eye level, but I positioned myself to appear as if it were taken from above.
The scenario in my mind at the instant the photo was taken is that I am in the wilderness when a large predator suddenly appears on the trail ahead of me. I am confident rather than scared, but am engaging Ti to decide the best course of action. There is an adrenaline rush, which I was actually able to sense slightly by putting my mind into the scene. I suspect that the slight adrenaline rush activated the fight or flight response in various brain regions, and this resulted in somewhat of a "fight" expression due to engaging Ti and deciding to face the predator rather than escape. Doing this had the desired effect of creating an intense Ti expression, but also one which was complicated by a hint of aggressive annoyance.
Side note: About a week before I took this photo, I had a real encounter like this on the trail... with a skunk.
I was also very surprised that one person sent me a PM in which they were able to guess or intuit the expression being a reaction to a large predator.
Analysis of results
I expected more Ti primary or secondary people to perceive the expression as not angry because it's a state of mind familiar to them. That appears to be the case, although a larger percentage of Ti's than I expected indicated an angry expression. I also didn't expect the nearly equal ratio of both Fi and Fe being divided over whether the expression was an angry one.