jkovar - 9:01 am on Oct 26, 2010 (gmt 0)
I wouldn't block it unless it becomes a regular visitor.
Is the referrer Google News or Google Images by any chance? I know both have been experimenting with the data: protocol (which is what you've got there) for preview images lately, my guess is that a spider doesn't know how to deal with a data: URI and is applying the address found in a background-image for a preview to a base href generating that funky link.
That "obfuscated code" at the end is actually base64 encoded image data.