I use Photoshop Elements and here's how I create a PNG from a layout in order to create a quickpage where someone can put their picture behind the quickpage to get their photo(s) to fit just right in the place holders.
I receive jpgs from participants who could reate the PNG so the first thing I do is:
1) Open up the JPG in Photoshop Elements
2) Layer > New Layer from background
3) Take the magic wand tool and click on the photo placeholder area. You should see marching ants around the photo
4) Edit > Cut. You should now see a transparent section from where the section was cut.
5) File > Save As > png > Interlaced: none
And you're done!