Cheating way:
Basically, you would just find this line in messageindex.php
if ($modSettings['enableStickyTopics'] == 1 && $isSticky == 1)
$threadclass = 'sticky';
and under it do something like:
if($micon=='moved')
$threadclass='moved';
That would be ALL you needed I believe - just stick the icon in the images directory. It's a very cheating method but it should work (pretty much)
NOTE: This *wouldn't* effect anywhere else that the thread icons are used but I can't think of anywhere else they are used off the top of my head so
