You can just create a new category "featured" and add that category to the products you want featured (one product can have more than one category).
Then you can use that category in the parent category option of your featured module. If you don't want to see that category on a listing of categories on the front end, you can leave it unpublished and it will still allow your featured module to display its products.
There is an example of such module on our demo website if you need to refer to an example.
