Oh, I've got quite a few:
1. Don Bluth's visuals overall. That guys is a masterpiece, not just with characters, but also at backgrounds. I know he didn't do them himself, but still, kudos to whoever he hired to do it.
2. The wide shots. This is what really made this film stand out among Don's other works. Most of his other films had huge, crowded landscapes, like cities and stuff, with tonnes of characters milling about. But with this one, at times, Littlefoot and maybe one or two of the others are the only creatures in the entire shot, which I think gives it this really ambient beauty to it.
By the way, anybody notice that that little lizard thing that appears in every single LBT movie? First time we see it, it is checking out Littlefoot's egg, and runs away when he starts to hatch. And looking at all the films, he appears in every single one at some point. He's that little lizard ,usually a dark green colour, sometimes brown, with big black eyes and a little semicircular fin on his back.