ho provato così ma nn funziona!!!

codice:
public MioFrame() {
		super();
		contenitore=new JSplitPane()
		{
			protected void paintComponent(Graphics g)
			{
				super.paintComponents(g);
				Toolkit tk=Toolkit.getDefaultToolkit();
				Image imm=tk.getImage("percorso/cieloblu.png");
				
				
				MediaTracker mt=new MediaTracker(this);
				
				mt.addImage(imm,0);
						
				try{
					mt.waitForID(0);
					}
				catch(Exception e)
				{}
				g.drawImage(imm,1,1,this);
				
			}
		};