The MicroPython logos in the master branch currently have no license affiliated with them beyond the SIL license that was used for the text. The MIT license would apply to the source code/project as a whole but when used as standalone images (for blogs, websites, etc...) this isn't clear as the MIT license was meant for software, not art.

Considering this, if the logos are to be dual licensed, I propose for the logos to be used under the MIT license or optionally as CC-BY (which is the closest CC license to MIT license AFAIK).
http://creativecommons.org/licenses/by/4.0/
http://creativecommons.org/licenses/by/4.0/legalcode

The Debian project does this, which makes it absolutely clear what the terms for logo use are(but you will notice they use a more restrictive CC license that matches their code license):
http://www.debian.org/logos/

Here are other notable examples of how other projects handle this, some being unclear on licensing of the logos, yet provide guidelines or attempt to explain proper usage or what you cannot do with them:
http://qt.digia.com/About-us/Logos-for-Download/
http://www.kickstarter.com/help/style_guide
http://oshwlogo.com/
http://arduino.cc/en/Trademark/CommunityLogo
http://copyheart.org/
http://design.ubuntu.com/brand/ubuntu-logo
http://beagleboard.org/media
http://developer.android.com/distribute/googleplay/promote/brand.html
http://makezine.com/press-center/logos-banners/

I think having such a page on the wiki(or better yet, the micropython.org site) that provides this similar information would be good.