Dynamically Delete Files?

That does make sense. What specific help do you need?
If you want to change server side connectors, take a look at Server Side Integration documentation: http://docs.fckeditor.net/CKFinder/Serv ... ntegration, Firefox with Firebug should be also helpful.
Do you track somehow which files belong to particular gallery, perhaps they're stored in a single directory? If yes, it's just a matter of executing correct DeleteFile/DeleteFolder commands.

function myunlink($path)
{
  /*    make sure the path exists    */
  if(!file_exists($path)) {
    return false;
  }

  /*    If it is a file or link, just delete it    */
  if(is_file($path) || is_link($path)) {
    return @unlink($path);
  }

  /*    Scan the dir and recursively unlink    */
  $files = scandir($path);
  if ($files) {
    foreach($files as $filename)
    {
      if ($filename == '.' || $filename == '..') {
        continue;
      }
      $file = str_replace('//','/',$path.'/'.$filename);
      myunlink($file);
    }
  }

  /*    Remove the parent dir    */
  if(!@rmdir($path)) {
    return false;
  }

  return true;
}

//example
if ( !myunlink("/path/to/dir") ) {
  echo "something went wrong, check permissions";
}
else {
  echo "folder deleted";
}