To add an image to a fee that will show in the cart, at checkout and in the consent popup:
In your Shopify admin, go to Products.
At the top right, click the magnifying glass and search for the name of the fee. This will be the same title you used when creating the fee in the app (for example, “Delivery Fee”).
Click the fee product to open the editor.
In the Media section, click Upload New to add a new image, or Select Existing to choose one from your library.
Click Save in the bottom right corner.
Go to Content in your Shopify admin.
Select Metaobjects, then Fee, then the individual Fee.
Click the Select file button on the Image field and find the image in your library.
Click Done, then save the fee.
The image you add here will appear wherever images are displayed for that fee, including carts, checkout, and consent pop-ups.