Method SetIcon() accepts only image file name. Actual image file must be located in the text directory under resource directory. See documentation:
IconFileName—Specify the name of the icon file, including the extension. A valid format for the icon file is the PTC-proprietary format used by Creo .BIF, .GIF, .JPG, or .PNG. The new pane is displayed with the icon image. If you specify the value as NULL, the default Creo icon is used. The default search paths for finding the icons are: ○ \\Common Files\text\ resource ○ \resource ○ \\resource The location of the application text directory is specified in the registry file