For my unicorn, I got a black leather bridle to strap on. And, to give it a bit of color, I got a couple of red, blue & green rosets (which I all won myself back in the day, when I was a rider :b)
I will also get a black tank top for her later, that says "FUCK YOU I'M A UNICORN!" and with a white silouette of a unicorn I drew myself. :b
For my hybrid (Black-backed Jackal/Tufted Deer mix) I usually just use my orange jaegermeister flower necklace (like the rainbow ones people worn at EF19) around his head. :b