I was a bit furstrated last night when I tried to install the flash templates from paulvanroekel.nl because the installer was telling me it was completed yet I could not find the templatebs. After trying to figure it out for a bit I went back to the site and noticed I had missed the install instructions at the top right of the download page. I seem to like to jump into things and forget to read instructions a lot!
It turns out the installer is for Picasa 2.x and Google has decided to change folder locations in the Picasa 3.x versions. Now instead of being on your primary drive under Program Files >> Picasa the application is now located in C:\Program Files >> Google >> Picasa3. So if you end up running the installer you can just copy the files from C:\Program Files\Picasa2\web\templates to C:\Program Files\Google\Picasa3\web\templates and the new templates will show next time you export a folder or a single photo to HTML via the Picasa interface.
The collection of templates includes 19 in all including simpleviewer, tiltviewer, imageflow, highslide, lightbox, thickbox, and more. All of them are cool in there own way and can be viewed here.