I've reported other sellers before for using my photos from items that had sold - all were taken down within a couple of hours.

I used the report option in the other sellers' listing and it gives you an option to link it to your own completed listing by putting in the ID number.  It might be a problem if the listing is really old - I think they are deleted from the system after 90 days?  I haven't tried calling / emailing CS for photos theft, but would definitely try.

As a side note, I reported a seller who was using my photos to sell on Gumtree - quick response and removal also, with the added note that "Also we have blocked the photos so that they cannot be used to re-post."