What caught my attention was the inscription with the painting. It detailed how Anton Graff was part of a group friends who were known for belonging to a groups called the 'cult of friendship'. Within this group they regularly sent self portraits to each other.
So it seems the practice of profile pictures and sending them to 'friends' was a very old invention, and perhaps the progenitor of Facebook. New media does seem to extend what people have already done for a long while.