We have made a free to download cover image template for photoshop.
It includes the basics with both portrait and landscape frame and a simple callout line to get you started. You need photoshop to edit the files.
You can download the 1024×600 PSD file from here:
You can download the 1024×480 PSD file from here:
We are in the process of making some more templates in different sizes, but with the right skills you can easily customize the template to your needs.