We've dealt with painting Nurgle space marines. And what's with the rest of the starter - Poxwalkers? Here's a compilation of these awesome painted smiley guys from different authors
If you use natural shades, zombies are really grimdark. That better represents their nature than bright official colors. How do you think?
Pay attention not only to the painting but on the conversions. at the moment we have 10 starter and 5 boxed models, so, you'll need some changes to make the bigger army more unusual. Luckily, their background is totally OK with any kind of mutations.
Nevertheless, they are constantly smiling, they look really scary, especially if you pay attention at all the sore and inflamed areas.
By the way, plague zombies are now gone from CSM index. SO, if you have converted cultists, they also can represent Poxwalkers.