Moodle HQ has published a few videos highlighting the new features of Moodle 2.7. Check them all out at http://www.youtube.com/playlist?list=PLxcO_MFWQBDcxGul-CY1SiOke6Jkg2NPK
This short 2 minute video highlights the removal of standard themes and showcases both responsive themes, Clean and More as options for your Moodle 2.7 site. More’s customization settings are also explored.
Direct video link is here: https://www.youtube.com/watch?v=OUTzAFItLx4