Hi @mrsimons! Welcome to the community! 
If you looking to insert a whole file into Firestore using the Filepicker component, one way is to break the file object down into it's individual keys (base64 data, name, type) and insert them all into firestore:
You can also send up the JSON object by accessing the {{filepicker.parsedValue}}, this will send the full object and retain it's nested structure in Firestore:
If you're not looking to have a nested object in Firestore, it can also be converted to a string beforehand:
If you're not seeing these values being displayed, you can check the left panel to see exactly what's available:
