"Header"?

First, be aware that "header" has a very specific meaning in email and it's better not to use this word in relation to the content of your messages.

Second, the convention in email is to attach contact information to the end of your message. The standardized method is called a signature.

https://support.mozilla.org/en-US/kb/signatures http://kb.mozillazine.org/Signatures_%28Thunderbird%29

There are a lot of articles on the web about signatures in email.

If you really want to buck the trend and put in a "header" (I presume at the top) and really annoy your correspondents (because they have to scroll on down past it to get to the meat of your missive) then you could look at using a template or Stationery.

Thank you for you response ! I am indeed taking about embedded image in the top of the email part as shown in my picture (blue & red color image in rectangular). Please let me know the way forward if any.

Zenos has already given you the answer: use a template or stationery. Didn't you read that far?