Unused Avengers: Age of Ultron set designs reveal that the Avengers were to be honored for their heroics during The Battle of New York, and then Ultron was going to crash the festivities.
Originally, Avengers: Age of Ultron was going to feature a scene in which members of the Avengers were going to be honored for saving New York from Loki (Tom Hiddleston) and his Chitauri army. The ceremony would've taken place at Manhattan Park, with a monument erected behind them to honor New York's first responders.
In the images below, you will also see that monument destroyed with Ultron standing in the middle of the rubble.
Pure speculation: I'm assuming this would have been the original introduction of Ultron instead of having him appear at the Avengers' party, like he did in the film.
Embeds of Images removed by request. 3D set designs by Gregory Fangeaux.
When Tony Stark (Robert Downey Jr.) jump-starts a dormant peacekeeping program, things go terribly awry, forcing him, Thor (Chris Hemsworth), the Incredible Hulk (Mark Ruffalo) and the rest of the Avengers to reassemble. As the fate of Earth hangs in the balance, the team is put to the ultimate test as they battle Ultron, a technological terror hell-bent on human extinction. Along the way, they encounter two mysterious and powerful newcomers, Pietro and Wanda Maximoff.