Here are some custom-made Nurgle Plague Marines, complete with converted Rhino. These where achieved by using a pin-vice to drill some bullet wounds and an exacto-knife for armor chinks. The rot was made using standard basing flock and greenstuff.
Here is an image before painting to better see what was used:
And here are some finished ones. The painting was very easy as well. Surprisingly, they where done almost entirely with Goblin Green, White, and heavy use of the GW Wash kit. The entire army took about four days to do, not counting conversion.