Thanks for your question.
I have no idea if there are images of Mary Magdalene or of two of Jesus' brothers in a picture of the last supper. For one thing, any pictures painted of the last supper would have been painted hundreds of years following the event. How could the artist possibly know who else was there besides Jesus and the 12 Apostles?
Matthew 26:12; Mark 14:17; and Luke 22:14 mention only Jesus and the 12 Apostles. Any additions to that number by a painter hundreds of years later spring from that artist's imagination and not from scripture. Such imaginings are irrelevant to the serious Bible student.
I hope you have found this helpful.