The ItemName is used to construct the filename for the 90px icon shown. For example, providing "Unknown" as in the example below, the template looks for and loads "Icon_Unknown.png". If the image does not exist, it will show as a broken image. Be sure to spell things the same. For multiple-word item names, use a space between the words as per normal.
Example: The following wiki code
Will display an icon with link the item: