Bug 183900 Image in preview pane will not show until you reopen the "Edit Image Item" dialogue [0001]
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ImageBuilder.java
{
		inputArea = new Composite( parent, SWT.NONE );
		GridData gd = new GridData( GridData.FILL_HORIZONTAL );
		gd.heightHint = 80;
		inputArea.setLayoutData( gd );
		inputArea.setLayout( new GridLayout( 2, false ) );
	}
	private void createPreviewArea( Composite composite )
	{
		Composite previewArea = new Composite( composite, SWT.BORDER );
		GridData gd = new GridData( );
		gd.heightHint = 240;
		gd.widthHint = 315;
		previewArea.setLayoutData( gd );
		previewArea.setLayout( new FillLayout( ) );
		previewCanvas = new ImageCanvas( previewArea );
	}
	private void switchTo( int type )
	{
		if ( type == selectedType )
		{ 
			return;
		}
		selectedType = type;
		clearPreview( );
		description.setText( (String) descriptionMap.get( new Integer( type ) ) );
		Control[] controls = inputArea.getChildren( );
		for ( int i = 0; i < controls.length; i++ )
		{
			controls[i].dispose( );