Wanna finally get to the bottom of this. CKEditor, the rich-text editor, has an element whitelist. Any elements not on the list are filtered out when the editor loads, and it just so happens that images are not on the list. The function that loads the editor, CKEDITOR.replace(), has an object passed to it with additional configuration information; adding the following property to that object should prevent it from erasing images.
extraAllowedContent:'img[*]{*}'
Any img tag, any attributes, any style. It's a bit of a catch-all; if stricter conditions are needed, this section of the CKEditor docs should be helpful.