How to control what picture shows up on Finished art thread list?

Hi sorry if this is a dumb question, but how do I control which picture shows up as the thumbnail in the thread list when you have more than one in your thread post on the finished art section? I tried reordering them and it didnt do anything.
Thanks!!

The first attached image in the first post of the thread

If you are referring to your thread https://blenderartists.org/forum/showthread.php?423771-Linkboy,
looking at the order the images are attached you see


Which matches with the thread thumbnail


So there’s no way to change it once it’s posted?

Re-attached images in correct order so should now show the final image as the thumbnail



You can edit your first post and change the attachment.