as far as I know you cannot do that.
You need to edit your image in an image manipulation program such as paint shop pro, or photoshop, and create an image that is twice the width of your original image, and copy the original onto the new image, mirror it, then paste the original again, creating a seamless tiled image.
If you cannot get it done, drop me an email with your image and I’ll do it for you.
email me: ccpsceo at gmail.com (replace at with @ of course)