I don't think those are old gens; I think they're the original sketches Faust had for each of the characters when she first pitched the idea to Hasbro.
Well, if you want to be exact, they are old generation ponies that were going to be the mane6 originally, so we are both right.
Pinkie Pie has Surprise, Applejack has Applejack (
), Rainbow has Firefly, Fluttershy has Posie. Rarity was something like Sparkle or some crap, and Twilight's old self/original design is her mom.
I feel like a nerd.