Where'd Tileset 5 Come From?

I was editing my house today when I realized that Tileset 5 is rather out of place compared to the other tilesets. For one thing, it looks more realistic; the items seem to be designed for humans; and it gives off a… “darker” vibe. Furthermore, I can’t remember seeing it in any of the Pokemon games.

But anyway, my question is this: where did the PMU staff get this tileset from? Is it really from a Pokemon game? Is it from some other video game? Did the staff make it themselves?

…Is it ALIENS?

It’s probably from one of the generic RPG tilesets that comes with Eclipse.

Edit: For further clarification, Eclipse is a RPG maker for Windows. PMU was originally made using Eclipse, but the engine has been revamped multiple times, most notably with the PMU 6 -> PMU 7 transition.

Oh, I get it. O: Thanks for answering!