Each image has an audio file with it. That explains a lot about the long loading. I guess a splash screen is needed to let people know what is happening. In my tests of the splash screen, however, it seems they do not close automatically when the first image loads. Am I stuck with guessing a load time?
Sadly the preload action of sounds is done prior to the load of the splashscreen.
Once your tour is built you can edit the xxx_skin.xml file and remove some sounds from the preloadSounds action.
We have to add some parameters in PTP that allows you to tell us which sounds should be preloaded.