A letter is not a picture, at least not in the way we generally talk about pictures – it can be graphically manipulated and re-imagined in almost limitless ways and degrees and still perform its function. For most things-that-we-call-pictures, if you even made a relatively small adjustment to it, it would be a different picture.
That really depends on your language system. What you say is true for alphabetic systems, but quite different for logographic (e.g. Chinese) or pictographic systems.
I don't think they're different enough to refute my point. You see Chinese characters in a great variety of typographic and handwritten styles, all able to be read by fluent people.
