I submitted a photo to Shutterstock. They rejected it, and I can understand why. I knew the image wasn't ideal in terms of most stock photography. I shot it in low light, and I had to crop it. I hoped that the emotion and storytelling within the photo would make up for the technical shortcomings.
I'll post the image below, followed by Shutterstock's feedback. If you're thinking about submitting your work, don't make the mistake I did. You're allowed to submit 10 photos per batch for review. When you get one approved, you're then good to go in terms of submitting. I mistakenly only submitted one image. You then have to wait for them to review it before you can try again. That said, Shutterstock replied quickly.
Response from Shutterstock: Noise / Artifacts / Film Grain -- Image contains excessive noise, film grain, compression artifacts, and/or posterization.
I appreciated Shutterstock's quick and informative reply. I imagine they get a huge volume of submitted photographs. Next time.