Have you tried the Coat of Arms Design Studio? There's a free version that works right in your browser. Fairly simple to use, but might not allow for some of the more complex designs. Depends what you had in mind, I suppose.
http://inkwellideas.com/coat_of_arms/free-version/
This is a really good program, and is the one we standardized on for creating the arms for our roster. It doesn't do everything, and doesn't at all address different types of "lines" other than straight (no embattled or wavy edges, for instance), so we often have to do some finishing work in photoshop.
The good news is that it will accept external images to use as charges.
I'll be happy to do a few photoshop mock-ups if you know what you want (they'll be imprecise hacks to save time, since it's not worth making it perfect until you've chosen).
For terminology and ideas for geometric shapes and the like, I really like this primer from the SCA:
http://heraldry.sca.org/armory/primer/ (for some reason, images don't seem to be loading at the moment)
Here's an archived copy of the page on divisions:
https://web.archive.org/web/20130620212111/http://heraldry.sca.org/armory/primer/fielddivisions.htmlArchived copy of the Ordinaries page:
https://web.archive.org/web/20130620232347/http://heraldry.sca.org/armory/primer/ordinaries.htmlI don't know of a specifically 6-field division, but there are divisions of 3 and 8, plus you can overlay ordinaries, such as a chief or base, that gives you an area to work with as well.
I'm trying to lightly steer people away from quartering, not only because it's heavily used already, but also because historically it most frequently was a joining of two sets of arms through marriage, which often is not what most people intend in our community.