If the Black Death or the equivalent hits the area, start making the large groups into roving bands of Flagellants, or a similar concept: large groups of roving doom-and-gloom preachers intent on some kind of public spectacle.
Another group to consider is merchant caravans. There's plenty of modules and suggested adventure hooks built around the idea of PCs hiring on as caravan guards, but the original books don't include them as a type of wandering encounter. I've actually got a merchant treasure type I've posted before that I'm currently tweaking, but you could use the Bandit as a template and add 2d6 x 1000 gp worth of trade goods for a quick implementation.
A lot of the other possibilities suggested in yesterday's post -- court or church officials acting as messengers, missionaries, emissaries from foreign lands -- are really more a matter of intention than stat blocks. There's usually an option for small groups of "classed" characters, which I'm sure we've all used mainly as rival adventurers; but why do they necessarily need to be adventurers? We could use a quick "mission roll" table to determine what a group of clerics, magic-users, fighters, or thieves are up to:
- Banditry (theft by violence)
- Violence (mission of vengeance or war)
- Adventure (standard D&D party motivations)
- Patrol (defending a nearby locale)
- Politics (internal or external message-bearers)
- Faith (missionaries or participants in a religious observance)