Thinking about it, Willow was a perfect concept for an '80s animated series. It had just the right mixture of magic and sword-fighting, adult adventurers for kids to look up to and - if you aged baby Elora Danan several years - a relatable kid about the same age as the target audience. Even the brownies were custom-made to fill the role of the annoying "comedy" sidekicks that every '80s cartoon had to have.
Lucasfilm thought so too, according to a set of concept drawings posted at io9. A Willow cartoon would have made sense too considering the success of the Droids and Ewoks cartoons that it looks very much in the spirit of. Check out the io9 gallery for drawings of all the major, familiar characters as well as new - if forgettable - ones like Generic Witch and Friendly Dragon. I actually like the artistry of these drawings a whole lot, it's just that the cartoon it suggests looks very by-the-numbers for that era.