Can we create editable banner in email template level (editable text on image keeping image link as variable input), if yes please let me know how to build it

Create a variable for the banner image link and use the variable in the HTML code. Following steps should work:

• Declare the variable in the meta tag:
  <meta class="mktoString" id="banner_link" mktoName="Banner Image Link" default="">
• Use this variable in the HTML of the banner image:
  <img src="${banner_link}" alt="my banner image" />

Or you can define this banner image as an element like below:

<div class="mktoImg" id="banner_img" mktoName="Banner Image" mktoImgLink="http://www.mysite.com">

<a><img style="border:10px solid red;"></a>

</div>

The second option will give you ability to select the image directly from the marketo's image library and also allow you to link the banner image to specific web-link.

Regards,
Amit