What is the correct file extension for Orange image embedding?
As r.kfr said: Import Images works with folders, not individual images. Place all images in a folder and select it for import.
Note that if you have images in different folders, Orange will consider each folder name as a class label for images.

Alternatively, you can create an Excel/csv file and define the path to the image. Mark it with meta type=image in the third header row. Here is how to define the header.