When housing prices seemed like they’d never stop climbing, developers were using architects’ names as selling points—but now they’re finding that Hollywood, and royalty, lend a dependable air of glamour even in a down market. So when Brett Buehrer and Jeremiah O’Connor recently completed a litigation-strewn, rental-to-condominium conversion of Manhattan House, a Modernist apartment block on New York City’s chichi Upper East Side, they settled on marketing the building not as a masterpiece designed by Gordon Bunshaft but as the onetime home of Grace Kelly.