Interesting. Do you have any book recommendations to add?
I was just reading about Pompey crucifying 6,000 slaves along the Appian way and--long before Constantine of course, but I may as well start back as far as possible.
If you haven't read them already, you should certainly investigate Eusebius's Church History and his Life of Constantine. Penguin publishes an affordable and readable translation, or you can read it on the web for free.