Braincramp - Need help with an icon.

Something more fantasy-ish than this might be better, and the lines certainly need to be stronger, but here's an idea that conveys size:

Wow I like that idea Fastlearner. I can see it with a simple creature like figure in three sizes, one inside the other. And you might change the fill from one to another to show size, but you can even change the color file for other meaningful properties.

Your post makes me think of those "relative size" pictures you used to see in National Geographic books - you know, the illustrations where you have the outline or silouhette of a man alongside proportionally-sized outlines/silouhettes of a mouse, a dog, a tiger, an elephant and a blue whale (for example).

In your fantasy setting, you could use say, a pixie, an orc and a dragon to illustrate the relative size. They don't necessarily need to be proportionally sized on the card - a pixie (think Tinkerbell) silouhette should get the point across that the creature in question is small, without also comparing it to the other two items. It's an iconic system that relies on the assumtions the players have about a fantasy setting - unless your fantasy setting is skewed from the norm, this should work well (and reinforce the fantasy setting).