A regular link gives you the following added features.

Added Features for Paid Listing:
    - Ability to add image or example of your photography.
    - Ability to add link to FaceBook fan page.
    - Ability to add link to Pintrest page.
    - Ability to add link to your Twitter Account.
    - Ability to add Google + Link
    - Ability to add Flickr Link

A Featured Link is a link that does not require a link-back, but is given a top spot in that category. Featured links are listed at the top of the category list, and will also be featured randomly on all pages on the site. (See right navigation for example.)

A featured link also includes all of the features of a Regular Link.