Shutterstock new images have always been performing well, but not in the past 6 months. Contributors are claiming that Shutterstock must had tweaked the search algorithm making new images getting less exposure. Or, perhaps bugs have been creeping through the site. But, I don't think those are the cases here.
Feeding the beast worked in the past because there were simply not enough of good images, then. When buyers could not get what they wanted in Popular, they will try to search through New. However, after years and years of uploading, Shutterstock has got enough of good images today. Buyers no longer need to search through the "irrelevance" New. We all know that searching through New is nightmarish due to keywords spam by contributors.
Here is a good example of why buyers no longer need to search New. Try to search for the keyword "seal" in Shutterstock...
... and under Popular, you can see all the seal vectors presented are good enough to satisfy the buyers. Buyers have no reason to search through New when Popular has enough of good choices already.
The beast is no longer liking the same old food. The beast wants to taste something new. Feed the beast with unexplored topics and I am sure they sell better than the seal.