Quick demo showing how to get a Base64-encoded thumbnail.png file from a gist.
Thumbnails are very handy visual indicators of the content of a block on bl.ocks.org, esp for rapidly surveying a user's collection.
However, many block creators don't add thumbnails because of the extra steps involved in adding them to a gist. Since the gist API doesn't let you upload binaries you end up having to clone you're gist to add a thumbnail. Note: @mbostock's gist to clone all gists is useful here.
It's been suggested that the gist-img shell script enables you to upload thumbnail images. That's at least half true. It automates the base64 encoding of png images prior to upload with @defunkt's gist CLI tool, so you end up u