Without knowing the game, guessing is all I can do. But guessing is fun:
- Perhaps the developer renamed "jpg" to "json" for fun and the files will actually open in an image viewer
Perhaps you misread "jpg" as "json"- Perhaps besides the json files there were folders extracted which contain images?
- Perhaps the developer put game data into the "images.rpa" file and all the things you actually want to look at into "donotopenthisboringfile.rpa" for fun
- Perhaps the developer encoded images with Base64 and stored them in json files
I'm out of ideas.