Sphere of Creation in Art

Very interesting pictures showing the sphere of creation in art.

Notice how there is a line across the middle representing in the earth in most of the images. It only becomes the globe earth AFTER the 1600's

https://artmirrorsart.wordpress.com/2017/04/09/mirror-spheres-or-adventures-of-globus-cruciger-in-flanders/

Representations of Our Lady of Grace are always identifiable because they present the Blessed Virgin open armed, and crushing the head if the serpent with her bare foot. Although neither a necessary nor universal part of the image, it is also fairly standard for Our Lady of Grace to be presented as standing on a dome, which is typically painted in powder blue, and often decorated with stars.
Does the dome thus represent the Firmament of Heaven?
Can anyone comment of the age and origin of the Lady of Grace image?

The dome is the firmament yes.
no idea about the age or origin of our Lady of Grace.
Welcome to the forum! Feel free to join our skype chats!