[Logician]

In the header find the image and replace it as a variable like:

PHP Code:

<a href="index.php?s=$session[sessionhash]"><img src="$mylogo" border="0" alt="$bbtitle"></a> 


Now edit global.php, find:

PHP Code:

eval("\$header .= \"".gettemplate('header')."\";"); 


Before that add:

PHP Code:

if ($forumid==X) 
{$mylogo='http://www.myboard/images/image1.gif';}
elseif ($forumid==Y) 
{$mylogo='http://www.myboard/images/image2.gif';}
elseif ($forumid==z) 
{$mylogo='http://www.myboard/images/image3.gif';}
else {$mylogo='http://www.myboard/images/image4.gif';} 


This will work when visitor's clicked a forum name and browsing through it, but will not work when they visited a thread in that forum since when visiting a thread $forumid variable is not set by vbulletin..