Retrieves or sets a value indicating the index of an Image in the Images collection,
which is displayed to the column's header.
|Long||A long expression that indicates the index of image in the column's header. The last 7 bits in the high significant byte of the long expression indicates the identifier of the skin being used to paint the object. Use the Add method to add new skins to the control. If you need to remove the skin appearance from a part of the control you need to reset the last 7 bits in the high significant byte of the color being applied to the part.|