Do remember that the martyrdoms which have the most lasting influence on Christian art, from St. Lawrence to St. Catherine [of Alexandria], rank from dubious to evidence-free; are there artistic traditions even of spurious martyrdoms of real people, like Clement and his anchor? (To avoid the obvious, I'm not discussing the Crucifixion; putting it under the head of persecutions of Christianity would be an original - although not unreasonable - synthesis.) This may belong in a section or subarticle on Roman Catholic culture, but not history; and I agree sourcing will be a bear.  PMAnderson