Similar to bug 26227, but for CustomCoverImages: it would be nice to be able to add a copyright statement or data provenance statement for CustomCoverImages. I would see this as a new HTML customization location "CustomCoverImageCopyright" where the Koha administrator could enter an html statement that would replace "Custom cover image" on the OPAC and staff interface. Having it as an HTML customization would make it translatable as well as having the possibility of including links back to the provider, if necessary. Since it's only possible to have one custom cover image source, there doesn't need to be an image-specific statement like in bug 26227.