This one will be going on the Cleric spell list page in the Grindhouse edition. By Eric Lofgren. (more of his work here)

James,
As I was falling asleep last night (in that half-awake half-asleep state) the following idea occurred to me. Then at 4:30 this morning I woke-up and couldn't fall back to sleep because of this idea. As I type this sentence it's 5:09 in the morning.
More than anything else, art in an RPG product needs to be useful. I think back to my early RPG days, and what "sold" me on a product more than anything else? Monster Manual-style art. The day I bought my Holmes Basic set, I also purchased the Monster Manual. It was a no-brainer purchase rather than the PHB or the DMG. Why? Because of the multitude of monster illustrations.
Some months thereafter I went to the store, money in hand, to buy the PHB. Ha! The Deities & Demigods book was sitting there, brand new on the shelf. One look at it (with its MM-style art) and there was no debate: I bought the DDG instead. I could sit for hours looking at the pictures in the MM and the DDG (and, in the next year, the Fiend Folio). The PHB and the DMG? Not so much. Sure, drawings of adventurers are cool, but how can they compare to the compendia of drawings of monsters in the MM, DDG, and FF?
Consider two monsters from the MM that nobody ever uses: the masher and the slithering tracker. (Hell, I literally never even noticed the very existence of the masher for about 20 years!) Why does nobody ever use them? What do they have in common?
No picture.
What if the interior art of Isle of the Unknown is devoted solely to Monster Manual-style (by that I mean relatively small drawings of just the monster itself) drawings of the 108 or so monsters in the book? That's a lot of drawings, but they'd be relatively small. The drawings would make the monsters come alive, unlike the poor masher and slithering tracker.
Plus, the drawings overall would be cooler than the drawings in MM, DDG, or FF. After all, how cool can a drawing of an orc or a brownie be? In contrast, all the monsters in Isle of the Unknown are weird and relatively hard to picture.