[Xenon]

try that:

open admin/functions.php
find

PHP Code:

        if ($avatarurl=="" or ($bbuserinfo[userid]>0 and !($bbuserinfo[showavatars]))) { 


replace with:

PHP Code:

        if ($avatarurl=="" or $forum[forumid]==x or ($bbuserinfo[userid]>0 and !($bbuserinfo[showavatars]))) { 


replace the x with your forumid where you don't want to show avatars..

then find:

PHP Code:

        if ($post[showsignature] and $allowsignatures and trim($post[signature])!="" and ($bbuserinfo[userid]==0 or $bbuserinfo[showsignatures])) { 


change it to:

PHP Code:

        if ($post[showsignature] and $forum[forumid]!=x and $allowsignatures and trim($post[signature])!="" and ($bbuserinfo[userid]==0 or $bbuserinfo[showsignatures])) { 


also replace the x