A lot of duplicate photos

Hello, Aden!
You are doing great work developing your API!
I am developing an iOS app as an my developer portfolio. It should become an open source social network like product.
While working on app I’m faced with a problem of getting a lot of duplicating photos in a feed, when I try to get random pictures without search params just in descending order. Is it possible to limit duplicating pictures? Or is it possible to make something like report function to report about inappropriate photo?