Although daemons of Nurgle are mostly straight forward to paint (green hues, sores, pustules, drybrushing, highlighting, and so forth), one aspect that I regularly wrestle with painting is the open backs on Nurgle daemons. Many of the modern Nurgle daemon range sports open backs where the spine is visible from beneath the skin (what could be more chaotic, right?).
I think the aspect that I most have trouble with is the colour tones. I want to reach for the bleached bone and get going on the bone bits that are protruding, and then accentuate them with gore. For the most part, this is not a bad approach and it produces good results I think, but it's not quite to the same standard that I managed with my (long-time to paint) highlighted plaguebearer. I think that some of the reason here is to do with the highlighting of the surrounding regions: perhaps more needs to be made of the skin flaps around the open back area. Rather than using gore tones or highlighted skin colours, I'm tempted to just go for dimly highlighted necrotized fleshy areas. Most of the highlighting on this chap is probably too high toned. Although the result looks grand on the tabletop amongst a pack of plaguebearers, there's certainly more that could be done.
If anyone has any tips about painting up open flesh areas in a Nurgle-esque kind of way, then I'd like to hear from you. Particularly if you've avoided green tones! What works for you? A gradual dull fade of the flesh colour (i.e. dark highlights), or something else.