I use this for changing a specific user. It goes in functions_showthread.php after line.
}
else
{
$avatarurl = '';
}

}

if ($post['userid']==##) {

header("Expires: " . gmdate("D, d M Y H:i:s",time()) . "GMT");
header("Last-Modified: " . gmdate("D, d M Y H:i:s",time()) . "GMT");
if ($dir = @opendir('{full directory path}')) {
$filecount=0;
while (($file = readdir($dir)) !== false) {
if ($file != ".." && $file != ".") {
$filelist[] = $file;
$filecount++; //Keep track of the total number of files.

}
}
closedir($dir);
}
mt_srand ((double) microtime() * 1000000);

$filebreak = rand(1,$filecount);
$filecount2=0;


while (list ($key, $val) = each ($filelist)) {
$val;
$filecount2++;
if ($filebreak==$filecount2) {
$avatarurl = '{relative path}'.$val;
}
}



}


Does anybody else do something similiar or have a better way to do it?