In addition to a talk: page, an editable image description page would be nice. The author could describe the image's copyright there, and also how the image was acquired/generated. (If some automated script was used to generate a picture, the GFDL arguably requires that the source code of the script be available, since that is the "preferred form of the work for making modifications to it.") This description page would also show the current version of the image and uneditable meta information (when uploaded, by whom etc.), and have a talk page attached. You would access it by clicking on an image.
If at all possible, the history of the image description page should show older versions of the image.
Like Brion said, we'd need another namespace: image: for the image image description: for the description image description talk: for talking
Axel