As usual, when selling your copyright you need to charge for every possible usage you can imagine for ever and ever in all media ever to be created. Check http://www.editorialphoto.com for guidelines about how to handle this sort of request, especially the forum, which you may have to subscribe to to look at the archives. Most people break out proposed usages, with a price for each (incl. time limit, size, etc.) and offer the prospective customer the opportunity to refine their long term goals in line with their pocketbooks. Depending on the uniqueness of your style, your reputation in the business, the nature of the image (famous person in the image), and the nature of the buyer, you certainly will want to know just what a full page 4-color ad in all world-wide editions of Newsweek costs, as that could be one of the usages that you'd want to have recompense for in advance. Most buyers want the whole kaboodle and when they find out that you value your work at the market rate, they discover that they want it for a year for local advertising, or to put on their web site for ever, or some such. It's very difficult to predict the use an image could be put to, and the money it could earn. Dirck Halstead, White House photographer under the Clinton administration, shot a political event back in 1999 or so and one of the hundreds of images he shot that day included a certain young, dark-haired woman with a big smile on her face, looking eagerly towards a certain president. Rumor goes that reuse of that image alone earned Dirck into the low 6 figures. Recently an exclusive usage fee negotiated by Corbis for Microsloth for a photograph of clouds in the sky earned the agency $135K, the shooter receiving 50% of that. Personally, since the image was used for the logo for Windoze XP, I think the shooter was paid too little. But those are a couple of ideas about what images can earn.
