Joe Stewart from SecureWorks has put together an effective "eye chart" that sources its graphics from sites that Conficker would block. If you can't see one or more of the images, you're either infected, or image loading in your browser has been disabled.
Firefox users can check if image loading has been disabled under Tools/Options and the Content tab. Load Images Automatically should be checked. Internet Explorer users will find it under Tools/Internet Options, then the Advanced tab. Scroll down to Multimedia, and Show Pictures should be checked.
