My educated guess would be a pack animal that would be used by the Ewoks? They did have horned pack animals in the 80’s cartoon and storybooks.
They rode ordinary small ponies in the tv-movies, but that may have been for budgetary reasons.
As for One Eyed Willy, it may be another Jabba’s palace critter that didn’t make the cut with George? There must have been a broom closet at ILM stuffed with rejected maquettes.