I'm going to try doing a little experiment with the tileset for my game, or in other words, the environmental graphics. Right now I'm just using the stock RPG Maker graphics for them, and that means if people see the game they'll immediately know it's RPG Maker. I wanted to get something more unique going, but I was laser focused on the idea of it being completely original and I knew I didn't have money for that kind of thing, so I skipped over the tilesets.
I wouldn't be able to drop in another paid tileset, because unfortunately it wouldn't be formatted the same way and I'd definitely be missing pieces that I need for all the current maps in the game.
However, watching some RPG Maker videos today, I actually got a great idea. I'm going to do a little bit of snooping around to see if I can find a tileset that can be used in conjunction with the stock ones. I could recreate the stock tilesets to the best of my ability with those ones that I purchase, and then any gaps could be filled with the stock assets since they'll mesh together well enough.
We'll see what turns up! I will definitely have pictures ready to show you all if I think it looks good :)