protected String[] listImagesInPackage(String packageName) throws SerializationException {
   // load package
   PackageItem item = rulesRepository.loadPackage(packageName);
   List<String> retList = new ArrayList<String>();
   Iterator<AssetItem> iter = item.getAssets();
   while (iter.hasNext()) {
     AssetItem pitem = iter.next();
     if (pitem.getFormat().equalsIgnoreCase("png")
         || pitem.getFormat().equalsIgnoreCase("gif")
         || pitem.getFormat().equalsIgnoreCase("jpg")) {
       retList.add(pitem.getName());
     }
   }
   return (String[]) retList.toArray(new String[] {});
 }