Your reason for the dealer not being able to provide pics makes no sense. He should have easily been able to get pictures of the parents if the breeder he is ordering from is reputable. I don't know of any breeders that withhold pictures of quality arowanas, or any other fish for that matter. They're usually quite happy and willing to show them off.
Pictures from other users and off the internet won't demonstrate what the fish will look like as an adult. That is determined by how the parents looked, and without showing pictures of the parents your just fooling the customer into thinking his fish is definitely going to look like show quality specimens, when it may not.
I haven't seen the fish or the parents myself, so I'm not going to help find pics of show quality fish when I don't know this is what the dealer is actually selling.
If you think this is ethical then you can easily search google images for pictures. But most of us aren't going to be willing to provide any.