you havent gone wrong, the file is there!
the webspace is set up so that nobody can see the directory lsting when they browse to your cgi-bin folder (this is a good thing). Type in the full name and path of the file in your browser e.g.
http://your.website/cgi-bin/picture.jpg
and it should display.
the 404 not found means it couldnt find a webpage to display to explain the error, because you havent made one yet

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oh yeah, and make a separate directory in the root directory for images, cgi-bin is used for scripts and things.