A very simple suggestion, aimed at spreading theme more evenly and making there be less competition for Jewel Beetles among Prophet Shop stuff.

Harbinger is about horses. Horses have nothing to do with locusts.
So why not move horse decors from Prophet over to Harbinger?

That way, you can finally get some pretty horses, without them draining JB away from Gnawrocks. Horses are quite expensive - 2 horses now cost you missing out on a Gnawrock, so barely anyone buys them. I still have horses from previous years Id like but never bought because Gnawrocks take priority.

But horses dont even belong in Prophet shop, they fit more in Harbinger shop with his Horses of Apocalypse theme!
15 ET for horse background
10 ET for an adult horse
5 ET for a foal

+4 to 6 ET for a "horse apparel" like halters and saddles, perhaps? (idea @ Skye Wolfe)
would be reasonable pricing for them!