>>38683760...I never noticed it was a mosaic of those two. Guess I'm renaming
I go by 3 factors:
Is the location recognizable from the games? If yes, they go under whatever gen they're the major region of(i.e. remake stuff still gets shelved with the originals).
Are there any recognizable people? If yes, it gets named depending on the gen of the latest-introduced recognizable human* present
If even then its still too vague and there's only pokémon to go by, it gets named by the latest gen pokémon present.
*Player characters cause special hybrid categories if there's protagonists from different gens and again the location is too vague
Example with pic related; The location looks really urban, enough to point to usual Unova illustrations. The image even implies Calem is out of his element too, so despite there being a later gen MC present, the region gets priority and the image gets named as such.