they had 'programmata' or electoral graffiti, i.e 'vote Gaius Julius Polybius aedile. He brings good bread' (bread was one of the things handed out for free at games, and is thus an example of the patronage system on a wide scale), abbreviations i.e. VB = 'good man', DRP = 'worthy of the public thing', they had satire ('all those asleep and macerius ask for vatia as aedile'. macerius = vatia). 27 scriptores are documented, thought to be an accepted profession (kind of like prostitution - for which there are also graffiti records, i.e. prices and pictures on the walls of brothels).
also they recorded the results of gladiator battles (i think that was the source in the CSSA trial this year).
erm, that's all i can think of off the top of my head, if you have it pamela bradley's cities of vesuvius may also have some stuff.