[ArcadeSyndicate]

hmm, you can try this...

add a new plugin (hook for example global_start) with this code

$templatevalues['forumid'] = $forumid;
vB_Template::preRegister('header', $templatevalues);

now you can use a new conditional that isn't availiable in vb4 by default.

<vb:if condition="$forumid == 1">

quick and dirty and also untested (i have no dev board at the moment) but now you should be able to add a different image to every forum id.