I prefer this mod to the others because it doesn't use any database queries

Depending on your forum size, this can seriously save 20-30 queries every homepage load.
You can fix the subforum issue by manually creating a hook in /includes/functions_forumlist.php
Search:
Code:
$templater = vB_Template::create('forumhome_lastpostby');
Add above:
Code:
($hook = vBulletinHook::fetch_hook('lastpostby')) ? eval($hook) : false;
Make a new file in /includes/xml/ called hooks_lastpostby.xml with the following content:
Code:
<?xml version="1.0" encoding="ISO-8859-1"?>
<hooks>
<hooktype type="lastpostby">
<hook>lastpostby</hook>
</hooktype>
</hooks>
And finally, go to your plugins and edit
Fetch Last Poster Avatars on Forumbits
Change the hook from
forumbit_display to
lastpostby (lastpostby)
Save, and your forum home avatars are fixed!
Hope this helps