I have an order for a large heart-shaped cookie with a unique request: she wants the skull and crossbones image placed on it. She requested a border with them, but is giving me creative license. Any ideas on how I would go about this?

Here's a link to the skull & crossbones cookies in the galleries:

http://www.cakecentral.com/modules.php?name=gallery&meta=search&type=full&search=skull&album=69&search_user=

Skull & Crossbones template:

http://www.clker.com/cliparts/1/9/0/4/11954356601633557489ryanlerch_skull_and_crossbones.svg.med.png

Or you could probably use a skull & crossbones cutter to cut out rolled buttercream for your cookies.

Everything you ever wanted to know about rolled buttercream:
(Includes recipes not found in recipes section and comparisons w/other hard frostings. Also hints and tips.)

http://www.cakecentral.com/cake-decorating-ftopict-221681-.html

HTH