I think this is a small niche -- people trying to sell photos online and that they are probably looking for information under keywords such as "sell photos online."
Though I did recently see someone looking for the service of getting keywords assigned to photos, at
http://forums.digitalpoint.com/showthread.php?t=249086 I'm wondering if you want to broaden your topic slightly -- to something like "Make Money By Selling Your Photos Online" or even "Increase Your Online Photo Sales."
When you say that no one wants to buy your ebook -- are you getting traffic and no sales? Or simply no interest and traffic? Also can you get any testimonials? Maybe if you gave a free copy to someone?
I know it is so disappointing to have something for sale, something of value and not get a response. Trust me, I've been there and done that!!