I dont see any reason why a second email would be sent unless the form is resubmitted.
maybe set a to to page in the universal email behavior to have it redirect to another page after the mail is sent to prevent the from from being submitted again.
the bcc (Blind carbon copy) and cc (carbon copy) are used to set additional recipients for the message to send copies to.
for the image to display in the email, make sure you provide a full url in the image src:
<img src="http://mydomain.com/image.jpg" />