Hi was having hard time finding out how to change the image in my email aswell.
After playing around with it managed to get it to work changing the code in the email notification.
First you wanna add the image file for the gift card to your files list.
settings> files> upload files
once image has been uploaded click copy link on right hand side of the picture you uploaded.
then go to your email notification,
settings> notifications> gift card created.
scroll till you find
and replace with:
<img src=“https://ADD COPIED LINK HERE/“width=“240” height=“160” alt=””>
SAVE
This is the only way i have tried which does not show my image blurred. You can also play with how big you want the image by adjusting the 240 and 160.
hope this helps others 