I quite like the icon by Nate Beaty that's listed as tip #2 here: http://net.tutsplus.com/tutorials/tools-and-tips/sublime-tex...

I actually kind of hate that one, ha. It's a little too...on the nose, we'll say, with the code in the background and the tabs at the bottom. I like my icons a bit more subtle, personally.

Another great one (imo!) is here, by Adam Kiss: http://dribbble.com/shots/378184-Unofficial-Sublime-Text-2-I.... A different take than the rectangular look, reminds me of Ommwriter a bit.