In the Android SDK documentation, all of the examples used with the @drawable/my_image xml syntax directly address images that are stored in the res/drawable directory in my
With the advent of library system, creating a library per big set of assets could be a solution.
It is still problematic as one must avoid using the same names within all the assets but using a prefix scheme per library should help with that.
It's not as simple as being able to create folders but that helps keeping things sane...