DIY and covetable. You would make it yourself if you knew how, but you don't, so just let the professionals take it from here.
What is it about headpieces, wreaths, fascinators, and hair "accessories" that aren't $2 barrettes from Forever 21 or plastic fake-diamond tiaras from Girl Props? Easy. They offer the opportunity to project a whimsical fantasy. Without, like, the extensive budget required to stow Rodarte and Erin Featherston orginals away your closet.
Pin one of these numbers onto your freshly-washed hair and you're suddenly an escaped wood nymph from some enchanted fairy-wood, a girl from a Francesca Lia Block story, an escaped Renaissance Faire (yes, it's a Faire) worker, or, whatever, someone with the balls to wander around the city in a pea coat and a crown made out of dried leaves, peacock feathers, and wooden vines. We love it when we spot them on the street.
Whichgoose has an excellent selection of medieval-meets-modern headpieces that can be taken as purely costume or the one necessary, label-less statement piece in an all-black outfit that's beginning to take on the drudgery of winter. She even quotes Dickens' David Copperfield to help set the scene for the potential impression you will make:
"She was more than human to me. She was a Fairy, a Sylph, I don't know what she was - anything that no one ever saw, and everything that everybody ever wanted. I was swallowed up in an abyss of love in an instant. There was no pausing on the brink; no looking down, or looking back; I was gone, headlong, before I had sense to say a word to her."