Header in email templates

I cannot find where to change the header in the email templates. All my email templates comes with our logo - fine - but on the right of this logo there seems to be necessary to have the text inserted in languages under email_site_name. I have copied an example. How to get rid of this in emails replies when you have your logo there already? Looks stupid to have both logo and this text next to each other. The email templates only have the body to change not the header/footer which could be useful.

I am looking for same thing as well, to make different logo to go with the email

you can change them in your template folder template/tpl/html_email_source.html