An evil sorcerer was a lord of undead before being forced to a long penance. He had a quasit bloodline familiar that didn't disappear with his alignment change from CE to CN, and continues to tempt and torture him. He thinks this is part of his penance.
Actually, the quasit was killed and now a mockingfey is the new familiar of the sorcerer. It has the Prankster archetype so it can keep its real thoughts and alignment hidden to its master. Sometimes, though, it has to take the form of a raven or other animal to "travel incognito".
Now, can the mockingfey assume the quasit's shape again by looking at an image of the quasit? It cannot assume the shape of a creature again "without a visual reference", but does that mean that it has to see the creature in the flesh, or is a portrait enough? Is there a magic item that could do the trick?
Since it names a "visual reference" rather than saying the original needs to be present - which would be more straightforward IMO - I figure yes, a good portrait should be good enough. Providing there isn't some noticeable marking on the side of the quasit not shown in the portrait that is.