While it could technically be considered cultural appropriation, it is unlikely to offend anyone, although Algonquins are still around and if you ever meet one then it might well make them either amused or very wary of you. The Algonquin tribes were the Cree, the Ojibwa, the Innu, and the Naskapi, and the descendants of the original tribes are still alive and well, living in Canada. There is also a small tribe in Northern Michigan in the United States, so they are definitely still around. That said, the Wendigo myth is probably about 4000 years old and known around the world, so the chances are that a Wendigo tattoo would be about as unoffensive to an Algonquin as a Dracula tattoo would be to a Romanian. The symbolism is more of a 'world-myth' now and so you can wear one if you like!