Apparently gulping the faded Polaroid makes it unable to open the door in depths which I guess makes sense since you can't put it in the door if you swallowed it :
What Happens At The End Of The Binding Of Isaac?
The Binding of Isaac: ReFlash - Modding of Isaac
Faded Polaroid - Binding of Isaac: Rebirth Wiki
Artist: ssimmot | ""Isaac & The Polaroid - Pt.3" | The Binding Of Isaac Gallery | Flickr
I have found what appears to be a faded version of The Polaroid - as a trinket : r/bindingofisaac