Before going any further, I'll describe the stock model he is based on, and the model for which he was created as an alternative.
An unaligned Fantasy Daemon Prince.
This metal Warhammer Fantasy Daemon Prince came in several pieces, and there were a couple variant arms, heads, and legs so the contents of a daemon prince blister pack would vary. The one from the official GW/Citadel image has a different right arm (a double-arm with crab claw) and different loincloth than mine started with, but is otherwise the same.
These Daemon Prince models displayed little or no iconography/features that implied devotion to any one of the four Chaos gods in particular and left that for the hobbyist to express through painting and conversion. I don't know when these were first released, but they were not new when I started playing (during 6th Edition).
I think the same models represented Daemon Princes in early40k as well. A 40k-specific Daemon Prince, wearing/partially-fused-with a suit of Daemon Prince-scale power armor was released eventually.
Some time later, probably the mid 2000's, a Nurgle-aligned Daemon Prince model was released (out of nowhere) for 40k.
I think it was in conjunction with the Cities of Death supplement, which contained more detailed rules for urban battles, but nothing specifically dealing with Chaos or Nurgle as far as I know. None the less, the supplement was accompanied by the only ever Daemon Prince model specifically aligned to a specific god, and a handful of other random ones for various armies.
Here he is:
Here's my take on the plague-ridden space-marine-ascended-to-daemonhood: