I've recently been playing adventurers exclusively (time constraints), and I used to get a mental image of the whole lycanthrope/troll/goblin/troglydyte/dire wolf groups running around the country side in groups. But that was when I was a noble and they're in groups.
Now when I'm killing them as an adventurer I tend to get a mental image of an anthromorphised money pouch. Sort of a cross between Kool-aid, a money pouch, a fluffy wambler and some form of pokemon. Don't ask me why, but that mental image settled in and has taken over my previous mental image of monsters. Now even in large groups I imagine them as groups of happy, fluffy, smiley money pouches ravaging the countryside.
Maybe the larger groups are the ones that banded together to form a bank. The damage they cause is merely an agressive marketing strategy being used on the peasants to put their hard work in production to good use. Which nobles hate, and therefore they send in the army. And banks and armies are way above my adventurer's ken, so are therefore off limits. It's the armies and banks that ruin an otherwise profitiable time for my adventurer, killing the happy-little-money-bag-monsters was great before they mobbed up into a corporate entity.
But before that time, yes, I am the slayer of small, felt purses
