Are your images made on a Mac using Adobe Photoshop 7.0 ? If so, the following may apply :

http://support.microsoft.com/default.aspx?scid=kb;en-us;817177

Image Files Do Not Appear When You View a Web Page with Internet Explorer 6 SP1
This article applies to…

SYMPTOMS
When you use Internet Explorer 6 Service Pack 1 (SP1) to view a Web page that contains image files, you may experience the following behavior: Some of the images do not appear on the Web page. Internet Explorer may no longer display images until you restart the program.

CAUSE
This problem may occur if you view a Web page that references an image that was saved from Adobe Photoshop 7.0 on Macintosh OS 10.