It has been my experience that when you move your pics to a folder with the .nomedia file, the gallery still shows the pictures. If you try to view any of the pictures that you moved, the gallery will not display them individually. Those pictures are not being rendered from the folder with the .nomedia file, but rather from the cache of the gallery. I call them "ghosts". These ghosts can be deleted from the gallery without losing them from the folder they have been moved to. Try it with a test picture. Download a pic, move it to your preferred "hidden" destination, go back to the gallery and delete the pic. Explore your hidden folder and select your picture. Done.