According to the Wintermark costume brief page, animal headdresses are appropriate for all kallavesi. To directly quote:
Headdresses are central to their identity as an individual and as a member of the Kallavesi and a symbol of their wisdom, power or responsibility. These are usually animal headdresses- either figuratively or literally as they believe it helps them draw on the animal’s strengths. Mystics usually chose animals associated with wisdom or guile while warriors favour strong animals like bears, boars and stags.
So a headdress as a symbol of power (since you’re a thane) seems thoroughly appropriate, just make sure it draws on animals that won’t mark you as a mystic. I’d suggest you steer clear of birds and feathers, and maybe go for a rough headdress crafted from a pelt, or a crown or headband that incorporates the tusks of a boar (obviously using antlers risks having people confuse you for a changeling). Something either clearly made from an animal hide or a simple piece of headgear adorned with some choice bits will give a kallevesi look without steering you into mystic or stormcrow territory.
I don’t know what other animals are appropriate for the mark, but if you do want to stray off the ones suggested in the quote I’d advise being sure not to use the other Varushkan virtuous animals (since they already overlap a fair bit) and not to use the mythical beasts that one would most closely associate with Dawn.