The splash screens appear when certain things have been loaded. If you wanted (for whatever reason) to prolong one of the screens, you would need to add a delay in whatever is being loaded at that time.
You can add a delay to the actual music by adding a short pause to the beginning of the mp3 file but other than that, it turns on as soon as it is loaded. Although I've never tried it, there might be a way of adding a temporary sound file to the music folder or playing a short sound file using a PY in the Arenas folder.
