Mike Aquilina (author of books on the Fathers — here and here) asked me if I had any info on a connection between Moses and Peter related to striking the rock from which water gushed forth (Ex 17:6). I have had fun looking into it and even have a thread about it on my Message Board.
I found this picture from the Catacombs of Callixtus with a description. I will post more as I get my "report" completed.
St. Callixtus Catacombs website says, “On the right wall of the arcosolium is represented Moses in the act of taking off his shoes. In the very next scene Peter strikes the rock in order to get water from it. A soldier, sword at his side, takes the water in his hand to quench his thirst. This soldier, as portrayed by the painter, is not Hebrew but Roman, easily recognizable from his uniform and weapons. Moreover, the features of Moses, who is striking the rock, are very similar to those of the apostle Peter. Moses is symbol of the ancient law, Peter of the new one. The soldier represents the first pagans converted by Peter.