The Animation Guild covers board artists who do continuity boards for animation shorts and features. The Illustrators and Matte Artists cover similar work for live action features.
There are a number of board artists who work in both live action and animation. (Dave Jonas, a longtime Disney artist, was adept at both. For live action, he boarded continuity for Mary Poppins and Robert Zemeckis' Back to the Future films. In animation, he boarded The Black Cauldron. Dave is also a talented watercolorist.)
Thing is, to be a live-action board artist on a union show you have to gain entrance to Local 790's experience roster before you can work. For animation, all you have to do is get yourself hired. There is no experience roster.
This gripes many animation board artists who would like to transition into live-action, and I'm often asked how people can make the jump. (Which is why I'm posting this. I think it's useful to get the answer out.)
There are pretty much two ways to get on 790's experience roster: 1) You work on a live-action movie that starts "non-union" and then gets unionized. After thirty days, you have the recquisite amount of time to get yourself placed on the roster. 2) You get hired on a permit that 790 issues when all other qualified members of Local 790 are engaged. After thirty days, you're placed on-roster.
Over the years I've gotten complaints from animation board artists about how the Illustrators' roster requirement has prevented them from getting a job. I empathize, but the Illustrators' rules are the Illustrators' rules, and what the various studios agree to with another IA local is out of TAG's control.
One bright spot: on a number of live-action films that have had sections of animation in them, Local 839 and Local 790 have (sometimes) shared jurisdiction. It's always a good idea for an animation stry board artist not on 790's roster to check to find out if the live-action feature you have an inside track on can hire you or not.