PNG Rejected : Reason - Similar Image(s) Already Submitted

[lakmal_4299]

I submited PNG images. This is the first time i submited this kind of images. But all of the images are rejected. The reason says : Similar Image(s) Already Submitted. Pls someone help me to understand this matter. 

[daniellei4510]

Many other contributors are facing this issue with similar rejections. Not a lot can be done about it except hope that the restriction eventually loosens up.