Why must custom map be a url instead of an image map in google drive?

[Haskell_F]

Is it possible to use an image map from my google drive? Why must it be a url? Why cant I use the shared link from google drive?
Since Position XY requires a jpg or png image, why would a url be required?

If the app is out of range of internet access, will this url be broken? Is there a way to store the url data offline such as google sheets?