Is there picasa photo viewer for kubuntu? I mean there are picasa, but picasa photo viewer, is it available for linux? There are menu in picasa to change photo viewer's file association, but after I associated them all, the pictures will still open with gnview or any other app on the list. It seems that there are no picasa photo viewer for linux.

I like picasa but it is not suitable as photo viewer. The picasa photo viewer however (in windows), are very light weight. Opens photos almost instantly. Superb zooming functionality. The other viewers in linux are still not that fast or the navigation is not as nifty as picasa photo viewer.

So, do I need to configure something or it is simply not available?

If you want to change the file association go to System Settings - File Associations and search for your image types, jpg etc. and change to Picasa if that is what you want.