One of the most weird stuff in the AtomPub specification is the media creation flow. First, you need to send a request in order to post the new media resource and once the response is correct you can update the media link entry related with it.
In order to avoid the second step, the Picassa team added to their api a new way to add photos, and now, they allow to send a multipart file that wraps the photo and its metadata.
This atom extension is been covered by an IEFT draft that Joe Gregorio published, and this morning I've updated the Abdera trunk in order to implement this specification.
You can read more into the Abdera wiki. Enjoy it.
