Here you can request deletion of an image. If you uploaded the image yourself, you can and should use the deletion URL provided after it was uploaded.
To notify us of a claimed copyright infringement you must use the DMCA process. More information on our DMCA policy can be found here:

This form is for images that at face value violate our terms of service (e.g. pages containing identifying information or Illegal content). Please provide us with Image URLs or Album URLs and a reason for deletion. For more than one URL use a comma to separate.

And also, if you’d like to submit content to us, use this form and we’ll get back to you. Be aware, there’s probably going to be a fee for doing so.