@maddyred Finally found some time to look into this. Not sure where you got some of data field names from. You better take a look at the code. Here you find the reference to the fields used for images: https://github.com/FOGProject/fogproject/blob/dev-branch/packages/web/lib/fog/image.class.php#L35
Just below that your also find the defintion of databaseFieldsRequired (for images) - you need at least those four to be able to create an image defintion: name, path, imageTypeID, osID
Here is an example with some more fields that worked on my tests:
... data = { "name": "fogsvos", "description": "API created image", "path": "/images/fogsvos", "imageTypeID": 1, # Single Disk - Resizable "imagePartitionTypeID": 1, # Everything "osID": 50, # Linux "format": "5", # Partclone Zstd "protected": 0, "compress": 9, "isEnabled": 1, "toReplicate": 1, } ...