I've started using various meeples from Meeple Source, as well as wooden doll bodies from amazon (the baby sized ones are about medium creature sized).
I use a marker or pen to number these - it makes it easier to keep track of hit points. I use them for most of the monsters they fight. Sometimes I color code them too - the green ones are goblins, the brown ones are bugbears, etc. They're cheap enough that I just buy a bunch and write/color/decorate them as needed.