I'm certainly an amateur photographer but take a lot of images around Cape Cod where I live. Really on a New Year's Day whim, I decided to submit some of them and see if any would get accepted. I only uploaded 15 images and more were accepted than not. The rejects were all because of commercial appeal.
Some of the rejects are odd. I had 2 close up images, one of a chipmunk and one of a rabbit. Chipmunks are apparently more commercial than rabbits.
I've spent time looking around at other's photos that are accepted. I certainly don't mean this in any offensive way, but there are a lot of amazing shots of things we all recognize, Eiffel Tower, Liberty, Opera House in Sidney, beautiful fields of tulips, lots of people on mountain tops, sunset, and sunrises.
I guess that's what sells, is there no room in stock photography for something different? I've done some Googling about good stock photography but I thought maybe some of you, already selling it, might have some advice or could point me at something I should be reading about the subject.