The woman on your shirt is wearing a poorly illustrated warbonnet. You can claim it is not fetishizing, but it is. Native women are represented in media only as primitive sex objects. We are not represented in any kind of respectful way. Tattoos of women are almost always sexualized; and though the woman character on your shirt does not have a body it doesn’t make it any less fetishized. We are not a character. We are not a stereotype.
If you want to celebrate the cultures that practice the use of the warbonnet then why not read works written by people from those cultures? Why not study their culture’s history? Why do you think that image does anything to celebrate those cultures? It is an illustration. It does nothing to celebrate those cultures. These cultures do not exist for your benefit. The warbonnet does not exist so you can use it’s likeness to make you look more spiritual/wild/free/etc. You really want to celebrate these cultures? Then respect those who are telling you to back off.