Hmm...very nice! I feel like this is a preliminary sketch for a project where all the Mane 6 gals appear in full-body pictures. Individual and/or all together, it doesn't matter; I would like to see each of them worked on, colored, and presented with clothes, hairstyles, poses, and different skin tones that match their personalities.
I think this has potential to be great. Nicely done!
Critique: Could use more variation on facial structure and body type. Also, nitpick: pinkie fingers don't tend to bend like that on their own, usually they pull the ring finger with it. Mostly I'd referring to Pinkie and Fluttershy. Rarity's hand is a bit off too. Anatomy isn't easy, I know full well. These aren't bad, but they could use more work.