Years ago my folk club used to run monthly theme nights - they were called "Folk-us Nights"! (Really original hey) We had songs about politicians, parodies, gold rushes, bushrangers (well we are in Oz), sailors, the weather, life in the city, you name it we probably had it. Sometimes the song's connection to the theme was a bit tenuous but that was all part of the fun.
Cheers
JennieG