When you post to Picasa, you now have the option to make those pictures open to all public searches or not. My guess is that you have them posted as private. I think that's where the https is coming from. When I post them as non-public, I can't even see the pictures in my Picasa web album. The only thing that shows up there are those that are public. I don't know how Google expects us to remember where the hell the pictures are placed.