Try Henderson's Vision and Image in Early Christian England.Cambridge, 1999.  There is a brief discussion about the use of Romulus and Remus in Anglo-Saxon art.  I believe that, in the later Middle Ages, it was fairly common practice for histories of dynasties or countries to trace their roots back to Rome or even to the Garden of Eden to secure their pedigrees.  Sorry, this is a little late for me but I would look at manuscripts.
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