Billboard revealed Tuesday that Nicki Minaj, Imagine Dragons, Wiz Khalifa and Kanye West will take the stage Sunday at the 2015 Billboard Music Awards.  The ceremony will take place at the MGM Grand, at 8 PM ET, with television coverage on ABC.   Previously announced performers include Van Halen, Mariah Carey and Britney Spears with Iggy Azalea.  Country/pop crossover star Taylor Swift, who leads all nominees with nods in 14 categories, will kick off the show with the debut of her music video for the single Bad Blood.  The star-studded video will feature Ellie Goulding, Paramore's Hayley Williams, Zendaya and Lily Aldridge, as the singer revealed with Sin City-like movie posters.  The latest stars revealed include actress Jessica Alba and Kendrick Lamar.