To use an image other than the available icon options, you can simply find the product created by Last Upsell - Post-Purchase in the Products section of your Shopify admin and then upload any picture. Once uploaded, you can drag it over to replace the current icon as the main image. It will then display on the pop-up.
To identify which products are created by the Last Upsell app in your Shopify admin, you can filter your product using the Product type lastupsell_generated.
This will apply to the following service offers:
Custom Gift Note
Premium Email Support
Unwanted Gift Return
First in Line
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