Ive seen some powerful blood and pleasure combos. Ive been thinking of it like a magic the gathering deck, mono color is strong but so is 2 or 3 colors if it combos each other well. Synergies are nice but things can work off the Meta rules too. Working together could simply be clanrats receiving the charge only to flee during your turn so your chaos knights are guaranteed the charge
Idk two furnaces lists are good too, quite a few pest battalions use it.. Bell might be worth it for future releases or even the fate change, verminlord if your not making a dice roll a 7.
Theres a alternative paint scheme for nurgle that uses more whites and purples, can't remember which GW book i saw it in.