The 170x154 are Facegens...that's their default size..
Real pics should be 170x255 in order to look good.
90x135 works and used to be the old jpg default size, but as you've probably noticed they are quite small in the profile pic..so it's a matter of personal taste really.
Real pics can probably be any size as long as that 90x135 stays proportional. If it isn't proportional, you'll get stretched or shrunk Height/Width pics..
