Connecting to an image has different behaviour than connecting to a shape. When I connect to a built-in shape, it’s trivial to connect to the edge. When I connect to an image, I can only connect to the center and the connection defaults to being on-top of the image.
Grouping an image together with a shape breaks the shape’s connecting functionality, so it isn’t a suitable work-around.
Ideally, I would like images to be treated as a sub-class of the square shape with the same interface. Alternatively, if I could create custom icons, this would also solve my problem.