I would go for like mettle front to the saddle. Like what you have collected so far. And leather for the back part. just put ridge in the bump where it changes from one thing to the other. about the animals skin.. humm don't know. I was thinking a lime green would be very DR. Suess but thin, maybe you don't want to go that far with the look. Maybe like a calico or palomino pattern with the colors on the skin?