Here are the backgrounds in there formal wear (well, most of them). From left to right: Cloudy Kicks, Mystery Mint, Golden Hazel, Paisley, Aqua Blossom, Rose Heart, Tennis Match, and Starlight.

Thanks to SelenaEde for the bases:
https://www.deviantart.com/selenaede/art/EqG-Cloudy-Kicks-Base-01-396594869
https://www.deviantart.com/selenaede/art/EqG-Mystery-Mint-Base-01-395258707
https://www.deviantart.com/selenaede/art/EqG-Golden-Hazel-Base-02-395894921
https://www.deviantart.com/selenaede/art/EqG-Paisley-Base-01-395167187
https://www.deviantart.com/selenaede/art/EqG-Aqua-Blossom-Base-01-396229797
https://www.deviantart.com/selenaede/art/EqG-Rose-Heart-Base-01-396229704
https://www.deviantart.com/selenaede/art/EqG-Tennis-Match-Base-01-396594706
https://www.deviantart.com/selenaede/art/EqG-Starlight-Base-01-395149648

The Background Girls belong to Hasbro and DHX.