I've been a fan of Brian Froud's artwork ever since he and Alan Lee did "Fairies." The comparison to Rackham is a good one, although Froud favors the grotesque more than Rackham did.
Wendy Froud (her name wasn't Froud at the time, but I forget what it was) was a dollmaker who designed and made models for some of the characters on "The Dark Crystal," which is how she met Brian, who was the conceptual designer. A few years later, their little boy, Toby, played the baby in "Labyrinth."
I''ve read one of the other Froud illustrated books you are talking about, BandSmurf. It was by Patricia McKillip, and I think the title was "Something Rich and Strange."
Years and years and years ago I came upon a picture book about the Black Death illustrated and (maybe) written by Brian Froud, but the title escapes me. Despite, or even because, of the grim subject matter, the pictures were wonderful.