You may embed a small image in HTML portion of the annotation using the data URL scheme as described in RFC 2397. Insert HTML tag of the following format with appropriate data from your image in the HTML annotation:

<IMG SRC="data:image/gif;base64,<base 64 encoded image data>" ALT="Company Logo">

Replace <base 64 encoded image data> with base64 encoded data for your image.

Please note that due to limitations on the URL length, this may not work properly for your environment and that some mail clients may not correctly interpret this property of the HTML IMG tag.

Symantec recommends using the more standard URI link for the IMG SRC property as this is more universally understood by internet email clients.

References
http://tools.ietf.org/html/rfc2397