[Delphy]

memobug,

What I did was set a limit of 10 threads if viewing thumbnails, or the normal 25 if viewing forums without thumbnails.

I agree with you on the user selectable thumbnails though - especially in the New Posts search screen. I hadn't considered a style becuase it would still do the mySQL queries to get the attachment ids even if it's not showing the thumbnails, unless you hardcoded the styleid into the php and checked against that.

To change the number of threads on a forum that has thumbnails:

Edit forumdisplay.php
Find the section where you define forumids

        $forumids = array(41, 43, 44, 45, 46, 47, 48, 49, 69, 70, 40, 50, 51, 52, 97, 98);
        if (in_array($forumid, $forumids)) {
                $displaythumbs = true;

BELOW this add:

                $perpage = 10;

Thats it. You could add this as a vBulletin option too.