The way you present your pricing structure is confusing. You should not list prints in with downloads. And, when you list image sizes you should provide both dimensions, not just the longest dimension.
Your design is unbalanced, both in Firefox and Explorer. The right-hand column (with the login, shopping categories, and shopping cart) should align at the top with the "box" that presents the image and its associated sales information. As it stands, that right-hand column is aligned at the top of the page and your corporate logo.
Prices seem a bit high to compete with microstocks, but I'm not a buyer so don't go by my impression.