If you scroll down the list of our personal blogs on the right you will notice that some of us have have our Imagi-Nation flags displayed instead of the usual "Blogger B".
You too can proudly fly your Imagi-Nations colors. While I don't know how it works for other blog program, most of us are with Blogger and I can tell you how to accomplish it for that program.
Go to your Dashboard. Find the "Layout" heading under your personal blog. Click on it.
In the upper left corner of your Layout you should see "B", the word "Favicom" and Edit. Click on Edit.
A box will appear asking you to upload a square image of less that 100Kb in size . . . which it will resize for your new favicom.
When it has done that, be sure to click the "SAVE" button and Blogger should do the rest.
I look forward to seeing more of us flying our country's colors.