I propose updating the Image line description to clarify the Title property is accessed via the field "label"
I.e., you change the title via: Dlg.Control("mycontrol").label = "my_image.jpg"
Image : When set to True the control will display an image file instead of a text string. The value of the Title property will be used as the pathname of the image to display (so in your script, you can load a new image by changing the control's title by manipulating the label field). The image will be scaled to fit the control automatically.