https://github.com/Esri/arcgis-experience-builder-sdk-resources/tree/master/widgets/use-assets
Here is the example Widget for using images or other assets. Pay attention to the folder structure and naming conventions to make it work properly.
JavaScript does not natively support xlsx, so if you want to do anything with your Excel file you will probably need a third-party package. A CSV file is lighter weight and easier to work with.
GIS Developer
City of Arlington, Texas