how to make your Xbox gamercard your RSS image
1. First you need to get an image version of your gamercard. i recommend the Xbox Live Gamercard Generator. use it to generate the gamercard of your choice.
2. Run your feed through FeedBurner, of course, and select the FeedImageBurner service on the "Optimize" tab.
3. In the "Image Source" field, select "Specify custom image url". In the "Image URL" field, put the address of your gamercard. you can make the "Link" point to anywhere you want. I used the Xbox Live profile page. Activate the service
(click for larger images)
4. View your feed image in Browser Friendly to make sure it is correct!