When the Metropolitan Museum of Art announced it was dedicating its 2027 costume exhibition to designer John Galliano, vintage dealer Johnny Valencia figured it would be a red carpet for the ages. Celebrities would show up in full Marie Antoinette drag, or squeeze into tightly bound corsets showcasing hourglass figures, recreating the pageantry of Galliano’s over-the-top runway shows.“There was a lot of excitement around this theme,” said Valencia, whose customers include the likes of Beyoncé and Rihanna. “There had not been this much excitement since camp” – the institution’s fete of outrageous and questionable taste in 2019.Valencia runs Pechuga Vintage,...