I am a huge fan of both Haze and Mackie's work. I like that for pretty much every vinyl release, you get the option of cover art by one or both depending on how many copies you want to buy!
I have a feeling the Melvins have fully settled in - Toshi records at Sound of Sirens, Mackie and Haze do art, Steven, Trevor and Pinkus play bass, Ipecac and AmRep put out the music, Walsby sells merch, Garth roadies.