Shutterstock has been a source of passive income to me and other photographers. It is exceedingly difficult to get onto the site in the first attempt. The first rule is to keep resubmitting until you get accepted.
Look at what’s been selling lately by doing a search on Shutterstock for keywords that describe your genre of images.
Shoot in RAW and perform a minimum of post-processing; nothing too creative. Work in 16-bit mode and Adobe RGB or ProPhoto RGB while in Photoshop. Convert to sRGB only when saving. Go over your images at 100% or 200% and fix any technical problems. Don’t lighten any images; you will just end up with noise that will lead to rejection. Make sure your images have enough contrast. If excessive correction is needed, choose an image with better exposure.
Down-sample your initial submission images to the minimum required size. This means re-size the images so they are no larger than smallest dimensions that Shutterstock will accept for judging the quality of your work. Once you are accepted, you can submit full-scale versions. Shutterstock is much more selective about the initial batch of images than they are after you are accepted.
Don’t submit nudes with your application. Shutterstock is a great place to license nudes (the kind that are used in European magazine advertisements to sell watches and shampoo), but your first batch should not include any. Vary your subject matter and setting too. Don’t submit all studio work. Don’t submit anything that has a logo, trademark, or other intellectual property visible.
When you are rejected, Shutterstock will tell you which images did not pass and why. Don’t try to fix these. Resubmit the images that did pass and replace the rejected images with new ones.