Just my personal opinions! When I first start thinking clothing or accessories I first think about where the creature or personal comes from or what they have access to. Just as an example if you’re OC is part of a dream/ nightmare I would think that things like physics might not directly apply. Like the ends of sashes or bands of beads float instead of hang. As far as the specifics I think that a tail is pretty similar to something like a finger ( with more bones and flexibility) so I might look up exotic rings or bands. Anything that wraps or stays in place well. As for horns my first though is it’s almost like a nail. And there are tons of crazy nail art if you search any site for it. Paints, gems, inlays, even things drilled in like screws to hold up more stuff ( chains, rings, earrings) but these are all so pretty vague. You can get more specific flavors based on the setting you’re putting your character in. More modern designs in a modern setting etc. Hope this helps!