Sorry but on my equipment with Pongo/Nextgen it works exactly as I indicated.
I take a photo with my cell phone of a place I want to save as a favorite, it is stored in the folder indicated on the path and when I want to use the Picture option to choose the image related to the Poi and the route is created.
If there is no entry in sys.txt it is not possible to perform this operation.
Or there is another option that I don't know about.