public class GraphSnippet1 {

    public static void main(String[] args) {
        Display d = new Display();
        Shell shell = new Shell(d);
        shell.setLayout(new FillLayout());
        shell.setSize(400, 400);

        Graph graph = new Graph(shell, SWT.NONE);
        graph.setBackgroundImage(new Image(null, "res/image.png")); //doesn't work!
        //g.setBackground(new Color(null,255,0,0)); //works fine!

        GraphNode n = new GraphNode(graph, SWT.NONE, "Paper");
        GraphNode n2 = new GraphNode(graph, SWT.NONE, "Rock");
        new GraphConnection(graph, SWT.NONE, n, n2);
        graph.setLayoutAlgorithm(new SpringLayoutAlgorithm(LayoutStyles.NO_LAYOUT_NODE_RESIZING), true);

        shell.open();
        while (!shell.isDisposed()) {
            while (!d.readAndDispatch()) {
                d.sleep();
            }
        }
    }
}

Graph graph = new Graph(shell, SWT.NONE);
graph.getLightweightSystem().getRootFigure().setOpaque(false);
shell.setBackgroundImage(new Image(null, "res/image.png"));

    Graph g = new Graph(shell, SWT.NONE);
    ImageFigure iff = new ImageFigure();
    iff.setImage(AB_BG.createImage()); //AG_BG is an ImageDescriptor
    g.getLightweightSystem().getRootFigure().add(iff, 0); //Add at index 0.