To change the scaling of the images in galleries to 'fit' the screen rather than 'fill' the screen, open as->bgswitcher->BGImage.as and replace the code from line 160 to 164 with the code below:
 
if ((mc.holder_mc._width > w) or (mc.holder_mc._height > h)) {
 if (w/mc.holder_mc._width > h/mc.holder_mc._height) {
  scale = (h / mc.holder_mc._height) * 100;
 }else {
  scale = (w / mc.holder_mc._width) * 100;
 }
}

Then publish fla->main.fla