First off, you did a nice job of catching the wind. Nothing better to illustrate that than Old Glory.

The thumb is inserted by choosing an image from the list at bottom right and then clicking a position for the image (right or left). I think if you don't click a position, the image doesn't show up. Maybe that is the problem, or maybe its because you have a Mac. :)  I notice that the list is only the last several images you uploaded. I used to pick up old images that I hadn't used, but can't do that any more.