. . . assuming you want the teepee to be the cake (and not just a figure on a cake??) . . . and that you are wanting a 3D effect . . . guess I would try stacking till you get the height you are looking for (and then carving to achieve the angles needed to "work") . . . and then use rice krispy treats to form the point . . . cover in fondant . . . and hand paint your designs or use fondant cut outs to decorate . . . http://www.fotosearch.com/comp/IHT/IHT104/tepee_~ih004009.jpg
If the teepee is the cake, use the wondermold pan (I think that is the name, it is the one you use to make doll cakes, hills, boobs, beehives) and you can cover in fondant.
If the teepee is decoration, use the long pretzel rods to form a triangle and cover in fondant with the flap open.
hth.
Judy
Debbie Brown has a cute one in her Easy Party Cakes book. PM me if you'd like me to send the instructions to you 
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