Unfortunately there is no direct way to sort gmail messages by Size, Sender, Labels, Subject. However, Abhishek has written a detailed report on how to achieve this using some workaround techniques.

And the rest of us, we should suggest Google to include this feature :

1. Login to your GMail account and click “help” and under “Help resources” click “Suggest a Feature” (or you can directly do it by going to “http://mail.google.com/support/bin/static.py?page=suggestions.cs&issue=116865&bucket=16935“)
2. You’ll find “Organization” section, click “Suggest it” for “Sort messages by size, date, sender, etc.”