Thank you so much (:
Two of the arabians I drew of the top of my head which is the 2nd and 4th one and I drew the thoroughbred off the top of my head, but the rest I looked at a photo to draw.
And yeah, I studied horses' muscles and bones a lot in my past so I know almost every place to shade and what it looks like. But sometimes I do mess up with proportion, but that usually happens from drawing at a certain angle too much without really stepping back and looking at it a bit before a draw it.
When I was younger I always had difficulty with the head, I would usually make it too short and the muzzle looked out of place, but I fixed that. Right now I still have trouble with the eyes some times. Usually I will put the eye too low or it wont be the right shape lol.