OPTION ONE: Leave the original music player notifications intact. The app will read its data and create a new notification with fully operational album art and media controls. There should not be any issues using the app this way, provided that the 'Use Broadcast Receiver' switch is disabled.
OPTION TWO: Block all notifications from the music players installed on your phone, and enable the switch at the bottom of the settings menu. The app will then obtain all its information from a BroadcastReceiver, and get the album art from either the external storage (if the song is being played locally) or from the last.fm api.
OPTION THREE: Somehow install the app on the system partition of your device, and grant it android.permission.UPDATE_APP_OPS_STATS. This is not possible to do from within the app as the UPDATE_APP_OPS_STATS is protected by the application signature. In other words, you will need to compile a new apk with the same signature as the rest of the system apps.
Unfortunately, this app is not compatible with every music player on the market. This is simply because there is no way for another app to obtain information from them about the current playing song.