I looked around for many months to find a good image system that I could run a specialised stock media website and found Photo Store Script and am very happy with it and also with the support provided by CMSaccount Inc. The system is easy to use from a user and admin point of view. A good selection of standard templates that are also very easy to amend but look very professional. Regular updates to the software are released and are available free to all purchasers via their control panel and now that these customer forums have also been setup, it is even better as we can ask questions and learn from each other.
As I also run the hosting company that I run my site on (Fetish Hosting) I can say that it is easy to install and doesnt cause any issues from a server hosting point of view either !