Note that I can not help you customize the week numbers. I have received so many requests and I do not have time to help everyone! All the help you need is on this page and in the documentation that Google provides. Please do not email me about this.

I have just updated the icons to a new set of icons submitted by Marco Baumgarten. These new icons look a lot better on backgrounds other than white, like when using the Firefox addon Google Redesigned. We are planning to release a new calendar with a new set of icons as well. Send any feedback to me.
I have also noticed that it is now very easy to add Google's week numbers. Read the section above.

I have just made a gadget for Google Calendar. Read the section above for more info.