The Arnolfini Portrait, 1434

This is another painting from the National Gallery in London, with the painting to the right and a detail above.  It was painted by Jan van Eyck with astonishing realism.
A couple stands hand in hand, in a room illuminated by daylight from an open window.
The identity of the couple is most likely to be Giovanni Arnolfini and his wife, Giovanna.
The man wears a large, broad-brimmed hat and an exquisitely painted fur-trimmed and lined velvet tabard, while the woman gathers a sumptuous fur-lined green wool dress to her stomach; its long train folded at her feet.
Dressed in the latest fashion, the couple are surrounded by objects that denote wealth: the oranges on the windowsill and chest, the gleaming brass chandelier, and the bed with its elaborate rich, red hangings.
The striking convex mirror on the wall behind the couple is also an indication of prosperity. However, its presence is more than symbolic. Reflected in the mirror, painted with remarkable precision, is an intriguing image: It shows the back of the couple and two figures beyond, one dressed in blue and the other in red, entering the room through a passage lit by an open window.
The figure in blue appears to be raising his arm, possibly in greeting. Above the mirror, written on the wall much like graffiti, is the phrase 'Jan van Eyck was here, 1434'. Oddly humorous, or self portrait?