NOTE: The monster images are scaled 200% in order to be more visible. Max monster dimensions are 40x40 pixels. Also, no black outlines!
@Vinterrun: Looks cool, I will edit it (remove outline and scale it down). You can also do this yourself!
@Salmoneous: The first one is like my Giant monster
I think I should add the rest as the "angry city mob" monster family
In general there are monster families, ranging from weak, common members, to ultra-powerful, ultra-rare members. Take the skeletons for example. The family is something like:
skeleton < skeleton warrior < skeleton mage < skeleton hulk
What about drawing families of common mythology monsters? Cerberi? Hydras? Djins? Now that's a challenge!
As for me...well, I think I've lost count. Maybe it's about 128 monsters right now.