Your pictures look really good! I am not familiar with shutterstock but I hope you stay, people like you brighten steemit up! I think the quality score could work to score all types of posts. Clearly it is not realistic to make a program that scores how good pictures are but my main point was that a big factor of the score would be to score based on how a post does based on upvotes/comments relative to your other posts. if one of your posts gets double the upvotes than your others usually do, it is clearly a better quality post and should get some more exposure to a bigger audience.