There isn’t any built-in option so you would need to use custom CSS. Example:
.easy-notification-bar { background-image: url(YOUR_IMAGE_URL) repeat; }
You can learn more about the CSS background-image property here: https://developer.mozilla.org/en-US/docs/Web/CSS/background-image
Unless the background image is essential to the design, I wouldn’t really recommend it because loading images will of course slow down page rendering and decrease Google page speed scores.
And if you do decide you want an image background, since the notification bar displays at the top of the site you really should pre-load your image in the site head tag prior to your CSS being executed. This will help with rendering and page speed.
