Pinterest doesn't automatically delete images pinners have chosen as folder cover decoration (highlighted in red above)
following a DMCA take-down notice.
If you file a DMCA notice for an image, you'll notice that one of the two versions Pinterest fails to remove is the one that a pinner may have chosen to use as a folder cover image. That's right. They don't remove everything. Pinterest will force you to chase that URL separately.
If that wasn't annoying enough, the folder cover images are wrapped in script attributes that block Firefox from being able to fetch the image URL by right-clicking on it. A creator trying to protect their copyright not only needs to jumps through endless loops to get their infringed work properly taken down, he or she has to deal with a behemoth of a passive-aggressive organization working tirelessly against the rights of artists to retain the rights to distribute their own work. It's not in Pinterest's business model to give artists that don't want their images pinned any help.
While these images are smaller than full-size, they are mere decoration and lead nowhere, and making an image smaller doesn't automatically make it "fair use."
To find the URL of these folder cover images, you will need to view the source code. In IE, View>Page Source, and in Firefox, Ctrl U.
Search the page of code for the character string: uploads/cover and you will find the URLs of the infringing cover images. They are in this format: