Official image host for GitHub projects?

GitHub itself has a "secret" feature to upload images.

I read about this in a comment by GitHub's own Phil Haack:

I edit (or create) an issue and drag it into there and copy the resulting markdown into my post. It's probably an abuse of GitHub issues.

If you do it like this, the image will be stored on some GitHub server, and it will have a URL like this one:
https://f.cloud.github.com/assets/19977/1656110/a3f8b280-5b6d-11e3-818d-c06ab05bd613.jpg

Fastly is not an image host, it's a content delivery network. See their website and this CDN Planet entry.

If you peek at the source code of the README.md page in the MMDrawerController repository, you'll notice that the image aren't initially stored at Fastly.net.

Moreover, they're supposed to be served through standard http (ie. not https).

<p align="center" >
<img src="http://mutualmobile.github.io/MMDrawerController/ExampleImages/example1.png" width="266" height="500"/>
<img src="http://mutualmobile.github.io/MMDrawerController/ExampleImages/example2.png" width="266" height="500"/>
</p>

The links your refer to are dynamically rewritten thanks to the Camo tool.

This tool simplify routing images through an SSL host in order to prevent users from being warned by their browser about potential unsecure content as every GitHub.com content is being served over https.