Don't forget that many people think because they buy the photo, they bought the rights. If they hired you to take the photos, and you're working hourly, this is true, but I try to make it clear either that they CAN reproduce the art (aren't I the nice guy) or that I retain the rights to reproduce (and I give them the reason). I usually give them the rights to get my name out there if it's photos, but then, I usually keep my best paintings, so different purposes for me.
Again, hope this helps; I'm sure that as we develop as artists we can help each other with the marketing aspect.
al