Picasa Independent Album Exporter is a free tool which lets you export all the pictures from any Picasa web album with a preserved desired picture size and dimensions.
You can download all the pictures for the web album in three simple steps, given below
1. Point out the web album in your picasa web album
2. Choose the destination directory where you want the pictures to be downloaded
3. You can choose the default naming convention for the images to be downloaded from your picasa web albums