I've told the story a few times on HN about the "cheating" in my 2007 Digital Imaging college photography contest for the Digital Imaging program[1]. In our instance, we're a totally (brand new) digital program, and someone combined some framed and created a scene that didn't exist, they shot the scenes separately and combined them. Our prof told folks to f'off when they complained as it was well within the lines. I agreed. That said...

This, seems outside the lines. Entering a photography contest with work that isn't based in photography, that you didn't shoot, isn't in the spirit of the contest. A photograph is an image created by light falling on a photosensitive surface - Edit all you want, hell edit till it's not even the same thing anymore, but if you're entering a photography content, at least trigger a shutter. The Sony photography awards are very clearly based around photography as the fundamental starting point. There are lots of pure digital art contests to enter, so enter them.

[1]https://news.ycombinator.com/item?id=35020010