Turning a Picture into a Background

[Overlordjoo]

I got this from a screenshot posted by Bytales.
I had to photoshop it a bit, but now that all of the overlay stuff is gone, how do I turn it into a useable picture for a background?

I have used sunnart, and I have failed at using KGpanels a ton. Any help for this?

I know it needs to be turned into a targa? What else?