You can add this in tempalte description section by pasting code below to generated template code:
<img src=”ADD_HERE_YOUR_LINK_TO_TEMPLATE” style=”max-width: 100%; height: auto;”>
ADD_HERE_YOUR_LINK_TO_TEMPLATE – here you must paste your link to photo, you will need photo hosting or you can use ebay photo hosting after publish listing copy ebay hosting photo url.
This code add responsive photo in section where you paste in our template.