Typically, the Salvator Mundi image of Christ is shown with an orb as a representation of His dominion over creation. But, this doesn't prove anything about the shape of the earth, and it isn't intended to. Later works, such as the Immaculate Conception image you have there, depict the earth itself as a sphere. Which is merely an artist's interpretation of the world being at Mary's feet or the earth as God's footstool.
It doesn't prove anything, really, as these images are not dogmatic pronouncements themselves on the shape of the earth. The Church has made no such pronouncements, only that geocentrism is true.