What did Paul the Apostle look like?

Last year an ancient watercolor of Paul was discovered in Rome, and last week it was announced that laser cleaning of the same 4th century catacomb revealed ancient icons of other disciples.  On the left is the watercolor of Paul and on the right is the icon of Peter.

These discoveries raise the question, what did the apostle Paul look like? The answer, of course, is that we don't know.  Neither his own writings nor the Acts of the Apostles, the two canonical sources of information about the ...