E-Commerce Configuration Guide : Site Configuration Settings : Item Settings : ImageTnPath
 
ImageTnPath
Key value:
Relative path to images
Description:
Used with the image column on the ItemList.aspx page. Path to the thumbnail image to use. Path is relative to the root of the web application (the virtual directory created when installing). ImageTnPath sets the path to the folder containing thumbnail sized images.
Example:
ImageTnPath = images/tn/
See also:
ImageField
ImageLgPath
ImageRel
Imagenodes