Interesting thread. Don't know if your interest is in trying to read early conformation signs, but I know I always find that very challenging to say the least!!
Here is a picture of Raven as a baby:
When she finally matured she'd kept her pretty head, nice shoulder and high tailset, but her back lengthened and she became less "square" if that makes any sense. However, she still ended up with 2 World Titles (open and ammy), 1 National title (only showed in open in AMHR), 2 World Reserve titles, many top 5's, many Supremes and Grands, Honor Roll every year and earned her AMHA Register of Merit (ROM) in open halter.
Here is a pic from her last show prior to retiring:
I have another mare, need to see if I can find her baby pic, that from that pic you would have thought she'd NEVER grow up to show and she ended up just one Grand shy of her HOF in halter as a 29" mare. Sometimes you just never know.