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/AttributePackage.java
* Returns the meta object for data type '{@link org.eclipse.birt.chart.model.attribute.TickStyle <em>Tick Style Object</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for data type '<em>Tick Style Object</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.TickStyle
	 * @model instanceClass="org.eclipse.birt.chart.model.attribute.TickStyle"
	 *        extendedMetaData="name='TickStyle:Object' baseType='TickStyle'" 
	 * @generated
	 */
	EDataType getTickStyleObject( );
	/**
	 * Returns the meta object for data type '{@link org.eclipse.birt.chart.model.attribute.TriggerCondition <em>Trigger Condition Object</em>}'.
	 * <!-- begin-user-doc --> <!-- end-user-doc -->
	 * @return the meta object for data type '<em>Trigger Condition Object</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.TriggerCondition
	 * @model instanceClass="org.eclipse.birt.chart.model.attribute.TriggerCondition"
	 *        extendedMetaData="name='TriggerCondition:Object' baseType='TriggerCondition'" 
	 * @generated
	 */
	EDataType getTriggerConditionObject( );
	/**
	 * Returns the meta object for data type '{@link org.eclipse.birt.chart.model.attribute.TriggerFlow <em>Trigger Flow Object</em>}'.
	 * <!-- begin-user-doc -->
	 * <!-- end-user-doc -->
	 * @return the meta object for data type '<em>Trigger Flow Object</em>'.
	 * @see org.eclipse.birt.chart.model.attribute.TriggerFlow
	 * @model instanceClass="org.eclipse.birt.chart.model.attribute.TriggerFlow"
	 *        extendedMetaData="name='TriggerFlow:Object' baseType='TriggerFlow'" 
	 * @generated
	 */
	EDataType getTriggerFlowObject( );