As a user I can probably answer those for you.
1. Yes
2. Yes
3. Standard way is domain.com/image/image.png
You could also use the image id instead of the file name or a combination of both. Think you could also change the routing so that first "image" word e.g. /image/.. is something else.
Basically, there is no "user" in the image url, it's identified and linked in the database.
Hope that helps 😉