If you didn't get the new wallpaper from the first beta you can get that one from here.
Check out What's New in iOS 8 Beta 3 and please follow iClarified on Twitter, Facebook, Google+, or RSS for the latest on iOS 8 and the iPhone 6.
● iPhone 2G, 3G, 3GS - (320x480)
● iPhone 4, 4S - (640x960)
● iPhone 5, 5s, 5c - (640x1136)
● iPhone 5, 5s, 5c - (744x1392)