I have a standard aplication. It uses resources - PNGs that are when programming in the DRAWABLE folder. They build up menus, buttons etc etc. ... Classic application nothing special.
And what I need to have is - "theme" support. Lets say I use this PNGs in my app:
The Drawable resources are packaged in to the application and cannot be modified. You idea of using an SD card will work (or you can use the applications sandboxed directory), you just need to manually load the png resources (ex.
As a note: If I ever open an application that immediately tells me to wait since it is downloading resources, I will force-close it and uninstall. Applications on Android, iOS, Windows, etc. should work right away without the need to download more resources. If you want a default "theme" then package it with the app, don't make the user download it (which will cause problems if the user is on mobile networks or doesn't have an internet connection when they open the app)