All we do is share links from the public forum, no different than Facebook.
The system would display whatever image was there at the time, but it still links to the actual thread.
P.S. Unless you are referring to the image at the top in which case it likely displays a random image from the top of the forum in the "Random Album Picture" area.
"No act of kindness, no matter how small, is ever wasted." Aesop