The thread picture displays on the right, balancing the postbit in available height, but a bit wider.
The thread author can upload the pic to go there and it resizes to fit (like uploading an avatar).
If the thread author does not upload, the display uses a default pic, assigned by admin per category or per forum.
The text between the two boxes is the preview snippet you see on a search.
Then the rest of the post follows normally, below.
s Later on I want just he TOP part of this post to display on a page to create a Latest/ Whats New type blog. Admin selects which forums feed this page.