It sounds like a related item to me. You're describing an image, that image is a resource which can be described by a MODS record, represented as a relatedItem, related to the original resource. The image license would be represented via accessCondition within the related item.
> -----Original Message-----
> From: Metadata Object Description Schema List [mailto:[log in to unmask]]
> On Behalf Of Saašha Metsärantala
> Sent: Tuesday, April 03, 2012 9:34 AM
> To: [log in to unmask]
> Subject: [MODS] Introducing the coverInfo element
> I would like to suggest the creation of a new MODS element, which could
> contain (or have an attribute containing) a URI pointing to a (scanned or
> born-digital) image of the front cover of books (or other items) described in
> MODS elements. Even other attributes could be really useful.
> A possible design could be something similar to:
> coverInfo imageURI="http://example.org/id54321.jpg"
> imageLicenseURI="http://www.gnu.org/licenses/fdl.txt" colorGrid="fff fff fff
> fff f00 fff 0f0 0f0 0f0"
> if we choose to use an empty element with all information in attributes.
> @imageURI contains the URI of the cover image.
> @imageLicenseURI contains the URI of the license applying to the cover image.
> Such information could also be included using RDF.
> @colorGrid contains a space separated list of the nine hexadecimal encoded
> average colors of each of the nine parts of the 3x3 grid covering the (book)
> cover. In the example above, the top of the cover is white, the bottom of the
> cover is green whereas the middle part of the cover is red with white fields
> both on the left side and the right side. Putting such information in MODS
> records would highly facilitate and speed up cover-color based retrieval of
> items, without the need for an extra HTTP request to retrieve the whole image
> and the following rework of the image information to make the cover colors
> searchable. Standardizing such a functionality would improve portability.
> I consider that such functionality can not appropriately be included in MODS
> elements such as "physicalDescription", "relatedItem", "note" or any other
> element available within today's MODS Schema version 3.4.
> Of course, similar functionality was not introduced in MaRC by Henriette Avram
> and we could question whether my suggestion can be considered being within the
> scope of what MODS intends to accomplish and the traditions behind MODS. Had
> this suggestion been technically feasible in the 1960'ies, it is not
> unplausible that it would have been introduced in MaRC then, I believe.