I like the idea of having a different background but in the two examples, the backgrounds were so eye catching it took away from the Aavegotchi. Maybe something a bit more subtle like a watermark or some kind of other identifier in the top right corner. How about a badge in the top right corner only for Haunt #1? If you start labeling each haunt it would take away from the uniqueness of haunt #1.
I agree that what distinguishes Haunt 1 Gotchis should be nuanced and artistic, be it a watermark or an identifier.
The design in the article is just a placeholder. Final design is not decided yet and it could also be voted(if there are multiple designs/community suggestions)