From 4D v15 R5, you can add an icon in the listbox header by programming. The image can come from a file, a picture variable or the picture library. This icon can be placed on the left or on the right side of the column.
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This feature is a powerful enhancement for the listbox object, providing you with a mean to define very flexible UIs. An array of objects can now be associated with the column of a listbox so that each cell can have different types of widgets according to the type of data to be displayed.