I only know of a couple of Italian families, so I can't really help much but perhaps you might wish to try your hands at some of their coats.
The Cajetani family, for instance, had a number of different banners. Initially, before a convinient marriage merged them with a northern Italian lineage, they had two waves on yellow field as their banner http://upload.wikimedia.org/wikipedia/it/a/a7/Stemma_Caetani.PNG
Eventually, after gaining connections in the north, their coat began a little more complex: http://web.tiscalinet.it/Amsit/stemma.gif
The Dukes of Gaeta (The Duchy from which the family took its name - Gaeta - Gaetani - Cajetani) had this: http://upload.wikimedia.org/wikipedia/commons/2/22/Coat_of_arms_of_the_House_of_Caetani.svg
very simply coat. Doubt there's even need to make it
When the head of the family led an expedition to the Balearic Isles, though, the Pope hadded two golden poles on red field to that coat, making it like this: http://upload.wikimedia.org/wikipedia/it/3/3a/Stemma.Gaetani.Pisa.jpg
Again fairly simple but historically accurtate and perhaps a source of inspiration.
Finally, there is a family called Tolomei which has taken part in three crusades and has "earned" the three moons by doing so. http://estense.cedoc.mo.it/info/img/stemmiimg/001/001-0203.jpg
I would assume, by the time of the mod, they either had none or only one? No idea exactly which crusades they partecipated to...
Again, hope this can give a little bit of inspiration to make players' banners, if anything!