Hi!

>Go to the TreeView, and, somewhere in the properties, assign the ImageList. That is to tell the TreeView where to get images from.

You can't make it using properties window. You need to make it in code, for instance, in Init event of Treeview control:
THIS.OBJECT.ImageList=THISFORM.ImageList1.OBJECT
This problem is explained in article "Q163803 - BUG: Cannot Set ImageList Property of Treeview Visually"