Here is a piece of rpg calligraphy that I did about a year ago. It shows what I use for monster miniatures in my games. I really like using the simple wooden cube to represent monsters because 1) it allows for me to really describe the monster without getting hung up on what the model looks like; and 2) they can represent anything. I need goblins? Break out the green cubes. Cultists? Time to grab the red ones!
I also really like using the larger monster meeples to represent bigger, badder, monsters because they are 1) bigger than the mini meeples I use to represent the player characters; and 2) the cool factor.