[Koha] Question on magazine local images

I understand that magazines are handled in koha under Serials / Continuing resources, with a record for the magazine, and one or more items for the magazine issues. I also understand that one may upload one or more local images at the record level. I wonder if/how may one upload local images at the item level, so that every item (magazine issue) has the cover image pertaining to the specific issue. TIA Manos Petridis