Load watchface background image from file system

As far as I can tell from the available sources, WFF allows setting custom background images, but only if this image is bundled in resources.

This is not enough for watch faces displaying user photos as backgrouds for example (which is pretty common and popular thing to do).

Please allow some option to load background images dynamically from external sources (e.g. file system's app's [private data folder](https://developer.android.com/training/data-storage/app-specific#internal)) or usage of sometging like large image `ComplicationDataSourceService` which exists currently.

If I'm mistaken and such an option already exists in WFF I would be happy if somebody can point me that direction.