The name of the field in the listname working list that contains a tree item's image path and file name, relative to the images directory, that represents an expanded node. Leave blank if using default images. This is only valid for unlevelled lists and will be ignored if listtype is "levelled".
Blank. Default images are used.
The name of a valid field, in single quotes. A list of fields in the listname working list can be chosen from by clicking the corresponding dropdown button in the property sheet.