Providing additional media resources (graphics / sounds) as billed in the Google Play application

In my Android application, which is available through Google Play, I want to offer additional items that can be purchased through billing in the application.

I would like to suggest items such as media content, such as graphics and sounds, which are usually included in the resapplication folder .

The problem is that these resources must be protected, of course. In the documentation, Google suggests not storing the contents inside the application package, but receiving the key after purchasing the product, and then sending the key to a remote server, where the key is checked and, if successful, the graphics / sounds offered for loading into the application.

Sounds good in terms of security. But if I do, I cannot use the content as easily as the resources are usually available. If the user can get additional background PNGs, for example, I cannot use R.drawable.new_background, but I need to decode the bitmap programmatically, right?

So, are there any alternatives or recommendations for downloading additional media content through billing in the application?

I would say, since everyone who is sufficiently defined can redesign the code, in any case, why not just store the content inside the application, but perform strong checks if the user can use this content at all.