Here is another mosaic from the Basilica in Washington, DC. This one is also from the Lithuanian chapel and is part of a larger collage of images representing the immigration of Byzantine Christians to the U.S.
Here, the mosaic portrays steel being poured, which represents Pittsburgh. Having family ties there, I had to get a picture of this!
"Slavery ended in medieval Europe only because the church extended its sacraments to all slaves and then managed to impose a ban on the enslavement of Christians (and of Jews). Within the context of medieval Europe, that prohibition was effectively a rule of universal abolition. "— Rodney Stark