Improve your average sales price with better looking photos.
Every year at eBay Live there are about a dozen vendors selling various lighting and photo box type solutions. Ranging from the $50 area up to the $2500+ area.
Obviously you'll get a better picture from a professional setup. However the solution linked to above should cost you $0.
If you're looking for something a little nicer but in the $50 range Marsha Collier the author of the eBay For Dummies series sells them on eBay: