And then I thought of totem poles. They're pretty modular in the sense that they consist of multiple (mythical) animals that are placed on top of each other. I'm pretty sure the (vertical) order is important if there is to be a particular meaning to the pole, but as an outside observer the order in which the totems must appear is not immediately apparent. So stamps of totems would serve my purpose well!
I found black-and-white designs, based on actual totem poles, on PaperTotemPoles.com. Perfect for making stamps of. I inverted the designs and started cutting.
Left, top to bottom: Thunderbird, bear, raven. Right, top to bottom: Beaver, octopus, whale. Yes, I know the scan is smudgy -- live with it. Trust me when I say that the stamps are much more impressive when seen up close. ;)
I wanted to use only designs based on real totem poles. As an example, the thunderbird stamp is based on the top totem of this totem pole, in Stanley Park, Vancouver.
The stamps are so big that a single totem pole made of them doesn't fit on a single A4 paper. I taped three cards together to make the totem poles that I sent to several people. For some people I chose the colors and order of the totems myself, but others I let chose the order and colors -- without telling them what they were actually choosing. Lots of fun, but a bit tricky to create lots of cards with different colors and different orderings.