I think it’s a great idea to make the icon configurable. That way, everybody can use what s/he likes.
(As far as the official logo goes, I like wizek’s idea of >< arranged in S shape. Representational without being literal. I may say, iconic
Incidentally, on Windows, it’s easy enough to change the icon of a shortcut, but to change the icon of the running task, you need to make an ICO file and replace the resource in the exe. So it’s a bit of a bother.