I think you could use tags and then create albums based on the tags. As long as you save your meta data to disk it will embed the tag in the photos and they should be there forever . it uses standard tags so they are recognized in programs that use them on a PC I’ve personally used Windows Live Photo Viewer and the tags are compatible. the only issue at the moment is if your photos are on an SD card f stop hasn’t yet released the Fix for SD card write access provided with the new lollipop operating system (at least on the htc one m8). It sounds like it’s right around the corner though.