  777    images/icons_forum     .

 config.php     
$bb_cfg['dir_forum_icon'] = BB_ROOT .'images/icons_forum/';

 index.php


$folder_image = ($is_sf) ? $images["icon_minipost{$new}"] : $images["forum{$new}"];

  

if(@file_exists($bb_cfg['dir_forum_icon']. $f['forum_id']. ".png")) {
			$folder_image = $bb_cfg['dir_forum_icon']. $f['forum_id']. ".png";
		} else {
			$folder_image = ($is_sf) ? $images["icon_minipost{$new}"] : $images["forum{$new}"];
		}

 viewforum.php



$folder_image = $images['forum'];

 
		
if(@file_exists($bb_cfg['dir_forum_icon']. $sf_forum_id. ".png")) {	
			$folder_image = $bb_cfg['dir_forum_icon']. $sf_forum_id. ".png";
		} else {
			$folder_image = $images['forum'];
		}

 /includes/functions.php

   

function icon_forums($forum_id, $param = false) 
{
    global $bb_cfg;

    if(@file_exists($bb_cfg['dir_forum_icon'].$forum_id.$param.".png"))
    {
        $return = $bb_cfg['dir_forum_icon'].$forum_id.$param.'.png';
    } else {
        $return = '';
    }

    return $return;
} 