I agree as well, it would be great for someone to figure this out and post a hack or mod. There are numerous people who would like to see this feature as well.
https://vborg.vbsupport.ru/showthread.php?t=68485
https://vborg.vbsupport.ru/showthread.php?t=68496
*Perhaps VB could think of putting in the next version. One thumbnail per thread, controlled in the admin control panel. TIA