Use a Greasemonkey script konwn as “Greasemonkey Scripts for Google Search” to personalize Google’s homepage and replace the traditional logo with a doodle of your choice. With the Greasemonkey script installed you’ll still see a new Google Doodle whenever one comes up. Your favorite doodle will be replaced by the new Google doodle of day.
If you don’t want your chosen doodle to be overrclassden, then you can select “Favorite Doodle -> Always show my favorite doodle, even on holclassays” option from the Greasemonkey menu. Right-click on the Greasemonkey icon on the status bar, then “User Script Commands” -> “Favorite Doodle -> Always show my favorite doodle, even on holclassays”. The menu options for this user script are available only when you are on the Google homepage.
To install this script make sure you have Greasemonkey installed. Greasemonkey is a Firefox Extension that works wherever you have Firefox.