Micro-Trains is having a photo contest which is open until November 1st, 2016. The winner gets their photo on the cover of the Micro-Trains product catalog, they get a framed copy of the photo, and they get $100.00 gift certificate. Unfortunately this is only open to N scale photos and I would assume Nn3 too.
In the rules there is mention that Z scale photos are not to be accepted. I would think Micro-Trains as a company would invite photos from all of their scales. Why differentiate between the scales when your company sells multiple product scale lines.
You can access the contest from their home page or you can go directly to the contest page
MTL Contest Page