So for retina devices you need to add the retina version of your pin with name pinname_2x.png in wp-content/uploads/year/month wordpress folder.
This is done this way:
Add the non retina pins in Theme Options – Pin Management.
And add the retina version of the same pins In Media – Add image.
It’s important this is done in the same month as when you add the web version pins.
Remember that the retina devices require the pin retina version name is pinname_2x.png (where pinname.png is the web version) and image should be retina format (which is double size). You can also use jpg files. Important is the name.
In theme pack we have also the retina versions of demo pins. Those can be edited as well in a vector editor, like Fireworks, I see you colored your pin with something custom so I assume you know how to do the same for the retina version pin. Change and save with the name above. Upload in Media – Add New. And should be solved.