Unless you're in business to sell billboards with a particular image on them - then it's print on demand and you need an EL - no EL needed. It's just a large ad, single copy
Print run or impressions means how many copies of a magazine or newspaper or brochure you produce. So if your image is used in a very successful book that sells 600,000 copies, the buyer needs and EL as it's over 500K copies