What's the significance of this Michelangelo reference?
Madoka's mother is drinking from a faceted glass and what your screenshot shows are two edges of it and the Michelangelo's painting behind the glass. The dialogue between two women doesn't really correspond with the painting's theme, as far as I'm concerned.

 

The painting seems to be part of the entourage of the bar. With studio Shaft in charge of creating this anime, you can safely assume that it's a subtle hint at one of the many existential topics raised in it. It's probably not very significant in relation to the plot, but it just may give you some food for thought.

Consider the process of Adam's creation by God a metaphor for a magical girl becoming a witch. As a more powerful entity, witches are capable of creating their own kind by corrupting magical girls. Something along those lines.