I'm slightly surprised it does that much.
From the procedure browser entry for gimp-image-new:
Quote:
Creates a new image, undisplayed with the specified extents and type. A layer should be created and added before this image is displayed, or subsequent calls to 'gimp-display-new' with this image as an argument will fail. Layers can be created using the 'gimp-layer-new' commands. They can be added to an image using the 'gimp-image-add-layer' command.
Then for gimp-drawable-fill: According to the procedure browser it takes a drawable as it's first parameter, but you are passing the image id, so you would need to have added a new drawable (layer) to fill?
Kevin