http://share.studio.adobe.com/Default.asp

Over at Adobe Studio Exchange someone has created an action that copies your horizontal photo and then turns it into a puzzle. I've tried it and it works.

If you don't know about Adobe Studio Exchange, its a site where designers exchange Actions, Files, Styles and other Adobe product related stuff. To use it all you have to do is register once. Make sure you rate the downloads. The designers appreciate that.