"Because Coatlalopeuh was homophonous to the Spanish Guadalupe"

Our Lady Of Guadalupe:  A Mexican National Symbol, by Brother John M. Samaha, S.M., provides an accurate and interesting account of how an Indian woman became assimilated with the "dark virgin" of Spain.  And the extensive Wikipedia entry on Guadalupe offers many details and images, along with a discussion of historical and interpretive issues. 

The Virgen de Guadalupe is traditionally depicted with an array of celestial symbols, as shown in this early representation.