When a user adds additional pictures to his own existing active listing, then the listing is showing active status. so admin not able to know the listing pictures are added newly.

example:

A user has a listing with one picture in active status,
then later he adds another 3 adult pictures, the listing 4 pictures are visible for all.
most classifieds website don't allow adult pictures.

How do admin know that a user added new photos?.

what i am asking is, when active listing pictures, videos are additionally added then the listing should go to pending status. (which is called as edited listing)
then it should go to pending status for admin approval.

is it possible to do for my general script.