If you want to go back to see all the previous cool customized Google logos, you can go here:
Some are for specific countries that you may not have seen if you just go to Google.ca or Google.com
For instance, republic day in Italy:
Or Jordan's Independence day:
Or Queens Day in the Netherlands.
Some Canadian ones like our Federal Election:
Some are even video's, Like Charlie Chaplain's Birthday:
I really love the Google Doodle's and how they change them. Very entertaining to look back on all of them.