Here's another way to get the url of the image directly from picasa
Follow these steps to embed a Picasa Web Albums image in your site.
1. On the My Photos page, click your album.
2. Click the photo you'd like to embed.
3. Click Link to this Photo on the right sidebar.
4. Set the following preferences:
* Select your preferred image size.
* Select 'Hide album link' to remove a link to the containing album, which is displayed by default with the image.
* Select 'Image only (no link)' to get the image URL by itself,
with no code linking back to Picasa Web Albums.
5. Copy the HTML (Ctrl-C) in the 'Embed image' field on the right-hand side.
6. Paste the HTML (Ctrl-V) in the source code for your site.