Bug 104986 Backgound image uses an absolute path
Currently Chart uses an absolute path to indicate a backgournd image, that may cause the design unusable on other environments. Expected the background image can be definded in multiple ways like in report designer. e.g. URI(absolute path), File(relative path), Embedded Image(Encoded Image Data).
chart/org.eclipse.birt.chart.engine/src/org/eclipse/birt/chart/model/attribute/AttributeFactory.java
Palette createPalette( );
	/**
	 * Returns a new object of class '<em>Polygon</em>'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return a new object of class '<em>Polygon</em>'.
	 * @generated
	 */
	Polygon createPolygon( );
	/**
	 * Returns a new object of class '<em>Rotation3 D</em>'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return a new object of class '<em>Rotation3 D</em>'.
	 * @generated
	 */
	Rotation3D createRotation3D( );
	/**
	 * Returns a new object of class '<em>Script Value</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Script Value</em>'.
	 * @generated
	 */
	ScriptValue createScriptValue( );
	/**
	 * Returns a new object of class '<em>Series Value</em>'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return a new object of class '<em>Series Value</em>'.
	 * @generated
	 */