Hi Brittany,
Earthbag is awesome. If you haven't already, I highly recommend that you read "Earthbag Building: The Tools, Tricks and Techniques" by Kaki Hunter and Donald Kiffmeyer. I was able to check it out from my local library and read it cover-to-cover. It was so useful I purchased a copy so that I could have it around for future reference and loan it to my friends. I haven't built an earthbag structure yet because I live in Vermont, and while the thick earth walls provide some insulating value, it is not nearly enough for a Vermont winter. I'm trying to figure out how to do a double-wall earthbag construction with insulation between, but that is not a pressing project.
You could certainly brick an earthbag building. You would want to leave a small gap between the earthbag structure and the brick, and tie the brick to the earthbag using brick ties. You should figure out how the brick ties are going to work with the earthbag construction. You might need to install them as you build the earthbag. You will also need to have a smooth "brick shelf" for your first course of bricks. This image:
http://www.imiweb.org/design_tools/masonry_details/details/01.030.0321.php shows typical details for brick for conventional construction. The vapor barrier shown in the image relates to the insulation, not to the brick itself - if you are not using insulation, don't worry about the vapor barrier.
Another option other than brick would be to protect your walls with a large overhang. If you are using a conventional roof, you can protect your walls from lots of moisture with large overhangs. This works best for single-story buildings. If you get wind-driven rain, the windward side will still see plenty of water.
--
Karen