Most of my email backgrounds are transparent. They are all on a 544x1060 background to help keep from tiling in a long email. A few of them are already on a solid background color due to the nature of the image. If the image is on a solid color background I have indicated which color under the link.
To use the corner backgrounds add your background color first and then the transparent body background. If you choose to use a background already on a solid color just eliminate the color back code. To add the transparent corner background to your email signature page replace the ( with < and the ) with>. Your html codes should be written like this:
(body bgcolor="color name or number here")
(body background="http:// address here" text="color name or number here")