[memobug]

Will there be one image for each forum, or one for most of them? If so, you probably want to append the forumid to the image filename, e.g. image_1.jpg, image_2.jpg and then load it accordingly. Otherwise if it's a smattering of images and lots of forums, you might use a switch:

switch ($foruminfo[forumid]) {
    case 5:
           $forumimg = "<img src=\"{imagesfolder}/bananas.gif\" />"; 
        break;
    case 9:
    $forumimg = "<img src=\"{imagesfolder}/apples.gif\" />"; 
        break;
    case 32:
    $forumimg = "<img src=\"{imagesfolder}/stringcheese.gif\" />"; 
        break;
    default:
    $forumimg = "<img src=\"{imagesfolder}/default image.gif\" />";
    ## or maybe 
    ## $forumimg = ""; 
}