Personally, I'm just fed up with Shutterstock.   They reject images that are my best sellers at other sites.  They reject entire batches of images for intellectual property reasons when there are no infringments at all and when no other site has a problem with them.  One photo which is my best seller on two sites was rejected for poor cropping.  One image was sent with a vertical crop and a horizontal crop and the one was accepted and the other one rejected saying it was blurry.  That was kinda impossible since it was the same photo.  I have close to 90% acceptance on four other sites and yet Shutterstock rejects almost everything.  I just don't understand their review process at all.