Some updated headcanon main six designs~  
Twilight) pretty much the same except I added hooves and a classic unicorn tail  
Rarity) changed up her hair and gave her hooves and the unicorn tail. Random headcanon that she dyes her hair every once in a while. Random but I like this headcanon for some reason  
Pinkie Pie) small horse  
Applejack) big horse. Tweaked her colors, markings, and hair  
Rainbow Dash) added hooves and headcanon that she later decides to cut her hair short  
Fluttershy) made her taller and tweaked her colors. Added flowers in her hair and headcanon that butterflies just like to land on her and she is just very welcoming to them
 
 
Older version here: fav.me/dcv8lsc