When browsed through your inbox with your Mail application, sometimes you need to flag certain useful email for future reference. With simple keystrokes, Shift Command L you can flag selected mails.

And now, do you want to change the icon of the flag as shown in screenshot below?

Mark As Starred

If you want to do so, follow these steps :

Change Flag Icon

1. Open your Finder
2. Go to Applications folder Shift Command A
3. Look for Mail application, Control Click on it and choose Show Package Contents
4. Once you're inside Mail package contents, follow these paths : Contents ▸ Resources ▸ flagged.tiff
5. That's the flagged mark with 16x16 dimensions. I recommend you to have a backup of this icon file
6. Find other image file that has 16x16 dimensions. If that file extension isn't .tiff, open that file with Preview and save as .tiff
7. Rename the file to flagged.tiff and replace the original flag mark

Change Header Icon

You will notice that even though you've changed the flag into other image, let's say star, the header is still displaying flag. For the sake of completeness, you need to change the icon file for the flag header also.

1. Look for file Mail ▸ Contents ▸ Resources ▸ flagged_header.tiff
2. The file dimension is 16x16. For better result, you need to set canvas size to 16x16 and have the displayed image set to only 12x12
3. As what you've done before, back it up and replace it with the new one

Now, you've got your new flag marking. The star icon I used in the example is taken from Famfamfam.com icons collection. For more small icons, you can also go to Pinvoke.com.

And here is the result :

Click here to download 2 new star icons and 2 original flag icons.