Im sure there are fake slab out there as with really anything of value. What Ive noticed from buying coins from photos is a lot of the time but not always the coin will have more detail then you can see from the photo once you have it in hand. This may be the case with the Morgan dollar that your concerned about. Like someone mentioned above it's hard to take good clear photos of coins.
The NGC slab looks perfectly fine. As for putting a fake coin in a genuine holder, that is a lot tougher than you might think. Normally you can't open the slabs without severely damaging them which would be easily visible. As to why you don't see a picture of the PCGS on the verification site they only include photos if the submitter paid for a TruView image, or if the coin is pictured in a Registry set. And they have only been including images for around three years. NGC has been photographing every coin they slab and including the images for over seven years now. (Unfortunately they have been slabbing coins for over 27 years.) So there are about 20 years worth that don't have images.
Yes even if the customer doesn't request images. For the past seven years NGC has photographed every coin they slabbed and the images have been posted on the certification verification page. PCGS no they only photograph on request for Tru-Views and for the Secure plus service. And only the ones where the customer has paid for Tru-Views (or coins in Registry sets with pictures) are put on the certification verification page. So the PCGS photo database is tiny compared to NGC's.