Recently I reported a bug with gist that should now be resolved. Testing it here.
404 error is gone: https://gist.github.com/raw/4455903/be4055af570f3e5c189f810712b515474aa68f76/spiral.svg
However, they've taken care to ensure that these images can not be linked in an img tag; see http://jsfiddle.net/2hGdj/
