Here's a better version of the Photoshop Action (works on CS3 and up for sure, prior versions I'm unsure) along with a blank template file:
http://www.mediafire.com/?ingmzejo3my
The above is meant to work for 176x248 images.
1. Open blank.png in Photoshop
2. Create a new layer and paste in your standard cover image
3. Stretch/shrink the standard cover image if necessary to fill the 176x248 layer
4. Ensure the new layer is centered and at the top of the layer list
5. Run the Photoshop action
6. ???
7. PROFIT
Edit:
You can, of course, resize the image after you're done to something smaller without losing quality. So, go ahead and shrink the final 176x248 image down to 160x224 if you really want.
http://www.mediafire.com/?ingmzejo3my
The above is meant to work for 176x248 images.
1. Open blank.png in Photoshop
2. Create a new layer and paste in your standard cover image
3. Stretch/shrink the standard cover image if necessary to fill the 176x248 layer
4. Ensure the new layer is centered and at the top of the layer list
5. Run the Photoshop action
6. ???
7. PROFIT
Edit:
You can, of course, resize the image after you're done to something smaller without losing quality. So, go ahead and shrink the final 176x248 image down to 160x224 if you really want.