ATTLIST Declaration Problem

I want to allow the <img> element to take an additional attribute called
"name". I have set the following declaration,

<!attlist img name cdata #implied>

but I am not sure whether I have placed it in the correct location, and, as
a result, the name attribute within the <img> element is not recognised by
W3C's validator.

Does anyone have any suggestions as to how to solve this problem? Thanks.

B. Ahmad