Gift card notification custom image - appears blurred

I am trying to use a custom gift card image in the email notification. Saved new file in assets, redirected it in the gift card script but no matter how I save, size or format (gif, jpg, png) when displayed in notification email, it is blurry. Can anyone help or explain to me why this is happening and how to fix? Attached is a screenshot of the issue.

Hello,

The image which you are using is of small size, please try by uploading any large size image.

Thank you.