I've had the problem more than a few times. There are some feeds that are just bad. No images, bad copy, etc. Yet some are great. The key is in selection and configuration. When setting up your feeds, use google reader to parse them as a test. You can also sometimes gain more content via making an atom feed using feedburner. Don't ask why. the real magic come from using Yahoo pipes. I've take feeds, and then built a query that reaches out to find images that are of similar use and or content it them permits those to be embedded into the feed for inclusion as a javascript into the tpl. You can see my versions here;
http://www.gotopianworld.com.
you can also go to pipes.yahoo.com and search for ithinqware227 to find my scripts.
enjoy.!