I just noticed that Google is testing image filters in Universal Search SERP. It seems like this filter will appear based on the search intent. If you are searching for ‘Meghan Markle’, it appears on Page 2. But Google shows the filter in Page 1 for ‘Long black dress’ as its intent for ‘image results are far stronger than the previous case.
Page 2 for Meghan Markle
Page 1 for Long Black Dress
For a product related “long black dress” search, Google placed the search filter on the 1st page, just after the paid search results.
Using the image filter without going to the Images tab would drive higher traffic to the images. This makes the case of optimising the images even higher priority now.