I really like the head swap on the helbrute. Along with the paint job it gives him a nice, strong Nurgle vibe.
The plague marines are looking good. Are they from the Dark Imperium set?
It's a mix of Dark Imperium, the supplemental push fit kit, blister pack icon, and the stand alone box. I found that mixing the various kits together gives you a nice variety, and no one looks out of place among the ranks. That and the "new" Nurgle stuff just looks awesome in general. The only grumble I have about the more recent GW kits is that the details and cool parts also mean it's harder to kitbash and swap around parts.