enum ImageIcons {
    BUTTON_OK_ON("path/xxx1.gif"),
    BUTTON_OK_OFF("path/xxx2.gif"),
    BUTTON_CANCEL_ON("path/yyy1.gif"),
    BUTTON_CANCEL_OFF("path/yyy2.gif");

     private  String path;
     private  Icon icon;

    ImageIcons(String path)
    {
         this .path = path;
        icon = loadIcon(path);
    }

     public  String getPath(){ return  path;};
     public  Icon getIcon(){ return  icon;};
    
     private   static  Icon loadIcon(String path)
    {
         return  ...;
    }
} 

... usage ...
 new  JButton(ImageIcons.BUTTON_OK_ON.getIcon()); 

 class  ImageCache {
     private   static   int  MAX_CACHE_SIZE =  50 ;
     private   static  Map icons =  new  HashMap();
    
     private  ImageCache(){};

     public   static  Icon getIcon(String path)
    {
         synchronized  (icons)
        {
             if  (!icons.containsKey(path))
            {
                insertIcon(path,  new  Record(loadIcon(path)));
            }
            Record record = (Record) icons.get(path);
            record.accessCount++;
             return  record.icon;
        }
    }

     private   static   void  insertIcon(String path, Record record)
    {
         if  (icons.size() == MAX_CACHE_SIZE)
        {
             int  minAccessCount = Integer.MAX_VALUE;
            String keyToRemove =  null ;
             for  (Iterator i = icons.keySet().iterator(); i.hasNext();)
            {
                String key = (String) i.next();
                 int  accessCount = ((Record) icons.get(key)).accessCount;
                 if  (minAccessCount > accessCount)
                {
                    minAccessCount = accessCount;
                    keyToRemove = path;
                }
            }
            icons.remove(keyToRemove);
        }
        icons.put(path, record);
    }


     private   static  Icon loadIcon(String path)
    {
         return  ...;
    }

     private   static   class  Record 
    {
        Icon icon;
         int  accessCount;

        Record(Icon icon)
        {
             this .icon = icon;
        }
    }
}

... usage ...
 new  JButton(ImageCache.getIcon("petya/xxx.jpg")); 

 class  IconMapping {
     private  Properties mapping =  new  Properties();
     private  IconMapping(String pathToMappingFile) {
         try 
        {
            mapping.load( new  FileInputStream(pathToMappingFile));
        }
         catch  (IOException e)
        {
           //create log record here...
        }
    }
    
     public  Icon getIcon(String name){
        String iconFileName = mapping.getProperty(name);
         return  ImageCache.getIcon(iconFileName); //см. выше :)
    }
        
     public   static  IconMapping getMapping(String propertiesFileName){
          return  ...; //как больше нравится, хоть new IconMapping(propertiesFileName)
    }
}

...usage...

IconMapping mapping = IconMapping.getMapping("myApp.properties");
 new  JButton(mapping.getIcon("frameXXX.buttonYYY"));

myApp.properties:
frameXXX.imageYYY=petya/xxx.jpg
frameZZZ.imageYYY=vasya/xxx.jpg