Our library recently switched from using Syndetics images for the cover images in our OPAC to using Amazon's free cover images. The cost? Linking to Amazon... The benefits = free, high speed image servers optimized for a global beating, item details, "look inside", more like this, etc...

Because III's (our OPAC provider) linking works by serving the first "standard number" in the catalog record, these links and images try to show up on every record that has a standard number, regardless of whether there is an image available on Amazon's server or not. So, I wrote a quick php gateway which uses Amazon's Associates Web Services to determine whether Amazon has a record of that item in their DB. Only if they do, does the script send the browser on to grab the image for the cover. Otherwise, it just displays a "no image available" image or a blank GIF (in the cases where Amazon has no information at all).