Comparing websites

After looking at Getty, iStockphoto, and Shutterstock, I'm getting a better feel as to what the submission process will be like. Before I wasn't thinking of charging for downloads, but the more I think about it the more I realize that's what it's going to have to do (which doesn't thrill me :). Getty didn't have any of their info on submissions available unless you completed 2 of the 5 steps, which I wasn't going to do. iStockphoto requires the image to be at least 1600x1200px, RGB, and only accepts jpegs. Shutterstock accepts jpegs, and has a ratio to determine if it's large enough. Basically at least a 2400x1800px image. My requirements will probably be at least 1600x1200px, only jpegs, and I'm debating over a review process. Obviously there will be terms of use, and if a user (photographer) uploads an image that violates it their images will be removed and their account suspended. I'm thinking with a button that allows for users to flag inappropriate content would be sufficient enough, since this site is really about the community atmosphere.