To display an image with your notification, insert an image URL into the ''Image URL'' field. The preferred image size is 500x500 pixels - this will look the best on the notification. Learn how to add an image to your notification. Here are a few webpages for free images and gifs to add to your notification:
1. Icons8
2. Gifer
3. Flaticon
4. Freepik
If you wish to add your own image to the notification, learn how to do that here.