Unable to add Logo in Email Body

In my development I am sending mails from SAP using the function module " SO_DOCUMENT_SEND_API1". But I am unable to insert logo in the mail body. As of now the mail body contains a HTML file. Added to it is a PDF file as an attachment to the mail.

I have uploaded the image in the MIME Repository.

Please guide me in adding image (logo) to the mail body using the above mentioned function module.