just hop on your dashboard and click on "View/edit/delete links"
From there, select the link in question and click on "edit"
You will be able then to select another image by clicking on the relevant
This may have happened because someone pasted as a URL the flickr page
which displays a slideshow instead of displaying the image itself.
If you click "Test link" it will open a new page to the URL where the image
should be found.
There, specificly for flickr, you can choose the "download" page:
which has links to all images.
You can use this as a URL for the link you are editing as all the images